Disclaimer: corrections much appreciated.

As I've mentioned before in a couple of discussions--Dragon Booster is, indeed, kind of racist. ("Has no doubt unconscious and unintentional biases in that direction, as do and probably more egregiously many other television shows created in the particular social context", if that phrasing makes you more comfortable.) It seemed to me very simple to enumerate this: if you're a man of colour in DB, your options are:
a) Subservient to the white guy of choice (Parm, Cain)
b) Subservient to the white guy of choice and stereotyped (Khatah and Sarjo the Asian Martial Artists, Kawake and Shaynn the black basketballers)
c) The sole exception, thirty seconds on screen and without a speaking part: Akarai.
And if you're a woman of colour, you aren't entitled to exist.

(I've sometimes fanonically theorised that it's only the lower cities which tend to be mostly-white, sunnier climates and darker skin being indicative of prosperity. After all, not all worlds in the multiverse are under contractual obligation to associate "honky" with "rich majority"... But that's purely a theory, and not canon-justified.)

But, for the sake of laying it out clearly at long last: here comes the proper enumeration of characters men of colour in Dragon Booster, by Crew (and making generous use of the Furox' trading card links). I'd like to also note that judging ethnicity by pictures only can be problematic in its own right; because the cartoon was made in North America/Canada, I am assuming that undifferentiated and pale cartoon faces are intended to belong to the majority ethnic group in those nations. I don't intend to claim that cartoon representations of characters of colour must appear extremely stereotyped to qualify as characters of colour. Apologies!

Penn Racing

Solely Parm, in sidekick's bond to rich white Artha. I was really expecting him to get a brief rebellious episode wherein Artha realises he should say an occasional thank you in return for Parm's long hours of hard work for which Artha receives the glory--but alas, he didn't, even though Artha takes him more for granted than Moordryd does Cain.

(Creator confirmation told us that Connor's "loaded", whereas Parm's strictly middle-class: the son of a teacher and a government employee. On screen, though, Artha and Parm seem to me to come off as equally middle-class.)

Dragon Eyes

Cain, inept minion with a duty to obey the rich white evil Paynns. He may be slightly better treated by his leader than Parm, though he's also less competent. His main use as a minion is being the Big Black Guy--and that's not exactly a role without its root in racist stereotype, though to me he does come across as a character who's developed beyond basic stereotype (exhibit A: cookies).

Other Dragon Eyes are Swayy, Blarre, Vizz, Rancydd, Prankk, and that random guy with the scar in the Council scenes (I assume he's Prankk). All white; I can see how the writers wanted to avoid at lot of Evil Black People On Evil Black Dragons, though I guess they already misstepped with Evil Black Dragons. (Seriously, although obviously humans're naturally skeerdy of the dark because we can't see very well at night, there is a bad history to the idea that black == evil!)

Dragon Flares

Pyrrah, Sparkk, Hazaard (who pretty much looks like Rancydd with snazzier clothes), Embyrr, Ignight, Blayze (finally! non-hawt woman! Too bad I don't think she shows up on screen...), Kindyll, and Flynnt. All white as far as we know, though Pyrrah, Sparkk and Blayze are supposed to be all related and thus have the obligation to share skin tone.

Grip

Mostly big white guys, unless they're female, in which case sexy underweight white girls. Phistus, Brawwnn (got a few too many double letters in the name there?), Clobber, Klynch (who could be a MoC), Kudgyl (if I may briefly digress into sexism, I really invite you to compare her figure with those of her male counterparts), Pummyl (love the white imperialist safari suit), Thumpp (the other woman on the team), and Mawwl (only mentioned on the reference sheet handout--ten-year-old kid).

Army

Wulph, Ambushh, Ferryt, Kwarry, Stalkrr, Synarre, Tagg, and Trackyrr. Caucasians.

Since Akarai's hair looked purple to me (I'm sorry--we just don't know anything about his draconium influence), I'll guess he's in the purple Academy House and discuss him here: he's on screen for about thirty seconds and has no lines. Granted, he's an exception in that he's a powerful character of colour who's nobody's sidekick, and in a series continuation I suspect he'd have had more to do--but he's really not much of an exception as things stand.

Inner Order

Yay, the Asian martial artists! Though a fair number of them look white. Which might be good in that, even though their leader is a stereotype, not all of them are--and bad, of course, in that there are Not Enough Characters Of Colour, also cultural appropriation. Judge for yourself:

Khatah (given the dignity of his name spelt wrong), Sarjo, Chee, Chukks, Dohjoh (Never onscreen as far as I know), Shurykyn (another skinny white girl), Zann (now tell me he's not a blatant stereotype), and Chyopp (only on the reference sheet).

Rant on Khatah: he was supposed to be this great racer who went to the Academy; his entrance has him snobby towards Artha--and then White Boy Moordryd beats him in a race, necessitating White Boy Artha to save him..and in subsequent appearances he gets rescued again and fawns all over Artha even while competing with him. It's as insulting as Kitt's treatment, though it's not in as many episodes: the great racer, reduced to subserviently cheerleading the rich white boy handed powers on a golden platter.

Rant on Sarjo: he has like one line.

There's also a fair-haired dark-skinned girl in blue I've occasionally seen in the background. Maybe I was wrong about women of colour existing in DB--they do exist, for about two seconds at a time!

Will

Kawake and Shaynn--black basketballers. Kawake starts out Misjudged obeying Word, then shifts to obeying Artha and Connor. Shaynn's briefly in a couple of Council scenes, and in the last ep lends his superior talents gratis to help Artha cheat win the Academy competition. (Is it cheating in a sports competition to surprise-recruit an Olympic champion to team up with you?) Artha needs someone to get him and his crew into the Academy--Shaynn volunteers his services even though he's never even seen the kid before. Your helpful servant Tonto! Ambition for Kawake and Shaynn is a choice between serving one white guy or another. I'm sorry, I could sound more ranty about this than I do.

(I do think it's nice that Kawake's a cool character in a wheelchair, though.)

Prophets

I think we've only seen Reepyr--white-green as a corpse. Glyff, Anr'key, K-OZ, Gavyl, Annk and Schizzm are the other dragons listed on the reference sheet with humans.

Keepers

Stewardd--pale, though I guess you expect it from underground-dwellers. Other humans listed on the reference sheet and never-seen: Seekrit, Shortcyrcut, Aysaff (possibly named after Asaph Fipke, who from Storm Hawks' delightful use of blackface and an entire species whose schtick is being big, dumb and brown I'd guess is white), and Arlynn.

Dragon Fish

White-as-underbellies Marianis and Dorsull. Styngraay's also listed.

Voice

Vociferous and Spynn, and some guy called Papaganda.

Mechanists

Rivett--white again.

Dragon Winds

Just Chute--and I might as well mention Spratt under this Crew section.

Other

Armmy, the chin of original Dragon Booster, Budge, Faiar, Faiar's Random Goons, chins of random Dragon Priests...inevitably white and male.

Also original Fire Booster, white female.

Malto--possibly non-white. Villainous and would therefore play into the less-than-educated non-white thug stereotype.

Random audience members--possibly a character of colour or two among them? Original Shadow Booster's covered face--well, we don't *know* he looked like Moordryd, right?

--

Overall Depresssing Tale:

Never more than about two characters of colour on a team that we know of, the one exception the Inner Order (and never more than two women, either). No named women of colour.

It's idiotic to compare racism to sexism; they're different things, though often practiced by the same kyriarchy, and arguing which one is worse draws attention away from opposing them both and/or is horrendously offensive to those who suffer from the prejudice being dismissed. I'm going to try to avoid doing that, and instead generally comment:

It's good that Parm is somewhere major in the plot in almost every episode. (Of course, Artha's not terribly appreciative.) Cain is also the most important Eye sidekick, and Moordryd is actually his best friend. They're visible, and fairly well-developed, characters of colour; since it's a kids' show, they're highly unlikely to get killed off, and Parm's booster-ing guarantees him a spot in the climax. But it is immensely problematic that there are no women of colour--I personally find that very egregious in retrospect, the stereotyping of Kawake and Khatah and the fact that there's so few characters of colour following pretty close behind that. There's only seven characters of colour with names given in the show out of a fairly large cast, five or so more scattered about on the trading cards and in the background, and they're forced by the narrative to suck up to the white guy of choice. While it's due to the general Mary-Sueing of Artha that everyone (even independent!Rivett!) has to tell him what a great racer and awesome hero he is regardless of whether they're competing with him at the time or Kitt's accomplished the exact same thing sans the same fanfare, that doesn't stop it from being especially problematic when combined with very real societal biases.

Comparing the seven main characters of colour to their white equivalents, male when possible:

Parm -- heck of a lot more plot-relevant than fellow teenage sidekick Kitt (and obviously junior sidekick Lance), though, compared to his best friend Artha, why couldn't he have been the hero? Aren't brains better than brawn? Does an awful lot for his white hero friend, doesn't often get thanked for it, and doesn't get much glory for it either.

Cain -- I can see why his character, reasons for it being fangirled though I can see, wasn't considered for main Neutral Evil Antagonist, and he's far more prominent than his fellow minor Eyes, male and female. Gets his Rebellious Episode, which isn't a bad reason why Parm didn't get his.

Kawake -- even though he seems older than white fellow Crew-leader Phistus and is quite possibly wiser, he's not the Council leader; he and Shaynn are in fact barely present, hardly getting a voice in Council decisions. In his victimization by Word, he's deceived by Word's lies rather than being mind-controlled like Pyrrah; less of his self is taken away from him, although set against that it is more his own fault. He's only really in one episode, unlike most of the other leaders. Needless to say: black basketballer.

Shaynn -- turns up as deus ex machina in the final episode just to help Artha. Unlike most other few-episode characters--Rivett to some extent, Chute, Kawake--he doesn't require rescuing by Artha. But he also doesn't do that much; that episode is all about Artha and Moordryd, and not at all about the introduction of Shaynn the Cool New Character. (Chute and Rivett garnered a lot more fan attention than him with reason.) He's treated like an inanimate prop; if Artha deigns to talk to him again, it'll probably be to ask and receive another favour. Granted, he's a character who wants to help out a friend of his brother's by doing what he does best--it's not wrong to have characters who do that--but a black character who exists solely to help a white character out of a jam is problematic. Rivett certainly had ambitions of his own, and though Chute did spend her ep fangirling Artha and putting down Moordryd for no particular reason, she did obviously make her own life in the prestigious Academy.

Khatah -- As decent as his initial snobby appearance was, he went pretty quickly to "Oh, Artha, you're doing so well beating that big bad Moordryd for me, and I love you so much for it even though I've been to the Academy already and should theoretically be competing against you right now!" (WTF is up with all that, Moordryd and Artha are supposed to need the Academy, they should both be pathetic novices compared to the people who've actually been there.) Chute has also been to the Academy and was imperiled by Moordryd and saved by Artha; though I think she comes off slightly worse against Moordryd than Khatah (against whom Moordryd had to cheat), at least she doesn't have to thank Artha for beating her in a competition. Rivett--a third character with an Academy history, and both white and male--is the only ex-Academy character who doesn't beg noble rookie Artha to save him from evil rookie Moordryd. Asian martial artist.

Sarjo -- barely talks. Compared to similar minor sidekicks: Dorsull, sidekick to a female character, has a solid racing reputation in his own right; Spynn appears to be a more capable fighter than Vociferous, if mostly silent and less important than him; Ferryt is at least more vocal than Sarjo; Pyrrah's little brother has his part to play. Strong n' silent isn't an uncommon character choice, and I guess Sarjo's lack of speech is a minor thing, but...

Akarai -- he's the most powerful modern character we've met, certainly more powerful than Sentrus, but he never gets a word to say for himself. Them's the breaks!

The powerful characters of colour beside him are the Crew-leaders Khatah and Kawake (two out of twelve; four out of twelve are women, though we only see a male stand-in for one). Otherwise, the in-show authority figures are Faiar, associated goons, priestly chins, Sentrus, and the Paynns. White (and in all but one case, male).

That Background Blue-Clad Girl -- compared to white equally-in-the-background Embyrr, at least Embyrr has a name!

Re: my little fanon theory--out of those known to inhabit or to have inhabited the powerful upper-city world, we get: Connor, Word, Sentrus, Chute, Rivett, Khatah, Akarai, and possibly Kawake, and the writers seem to have forgotten about Khatah (we only see him racing Down City, and getting beaten at that). That's mostly-white, especially considering the relative visibility of the first three, and come series' end it's the privileged white boys Artha and Moordryd joining them. If all the people of colour in Dragon City are up in Sun City, we're not really seeing it.

The summary is pretty accurate: the options are full-time sidekick to a rich white guy, subservient to a rich white guy, and silent.