Yes. The mixture is a metaphor allowing Melville to explore the unequal relationship between whites and non-whites in Melville's time.
It is worth noting that throughout the book, whiteness, in general, is used as a symbolism for evil. Moby Dick itself is white and Ahab believes the whale is wicked. Indeed the concept has an entire chapter to itself: chapter 42, The Whiteness of the Whale.
Another key theme in Moby Dick is the savagery of whaling itself. He does not shy away from describing the messy, awful business of killing and butchering the whale in gory detail. This is contrasted with the relatively egalitarian nature of the ship itself, where the crew pull together to survive the dangerous task and are paid according to their skill.
However, stereotypes persist. The mates are white, their harpooners are people of colour. In this, the equality of the crew is reversed because the mates are directly dependent on the harpooners. They may be in charge of a boat, but without the harpooner, they have no chance of catching a whale.
We see this rendered symbolically during a chase where Flaks literally stands on Daggoo. Daggoo invites him to do so:
Upon this, Daggoo, with either hand upon the gunwale to steady his way, swiftly slid aft, and then erecting himself volunteered his lofty shoulders for a pedestal.
“Good a mast-head as any, sir. Will you mount?”
“That I will, and thank ye very much, my fine fellow; only I wish you fifty feet taller.”
Whereupon planting his feet firmly against two opposite planks of the boat, the gigantic negro, stooping a little, presented his flat palm to Flask’s foot, and then putting Flask’s hand on his hearse-plumed head and bidding him spring as he himself should toss, with one dexterous fling landed the little man high and dry on his shoulders. And here was Flask now standing, Daggoo with one lifted arm furnishing him with a breastband to lean against and steady himself by.
This is an apt and very obvious metaphor for the way whites use blacks to their advantage. Indeed it's repeated in another white-black pairing: white Captain Ahab ominously treading the decks above Pip, the black cabin boy.
Melville makes additional use of the race contrast between whites and blacks to highlight the hypocrisy of the former believing the latter to be "savage". Starbuck, in western terms, is the most learned and "civilised" man aboard the ship. Yet in Chapter 59, Squid, it is Starbuck who is alarmed and turns to superstition upon sighting the giant squid (note again that the terrible squid is white).
As with a low sucking sound it slowly disappeared again, Starbuck still gazing at the agitated waters where it had sunk, with a wild voice exclaimed - "Almost rather had I seen Moby Dick and fought him, than to have seen thee, thou white ghost!"
"What was it, Sir?" said Flask.
"The great live Squid, which they say, few whale-ships ever beheld, and returned to their ports to tell of it."
By contrast, it is the savage Queequeg who understands the scientific significance of the sighting:
If to Starbuck the apparition of the Squid was a thing of portents, to Queequeg it was quite a different object.
"When you see him 'quid", said the savage, honing his harpoon in the bow of his hoisted boat, "then you quick see him 'parm whale."
Because, of course, Sperm Whales feed upon Giant Squid. Thus Melville neatly reverses the common tropes of the white scientist and the unlearned savage.
Finally, this theme is repeated through the character of Stubb. His behaviour, especially in contrast to the quiet and civilised Starbuck, is relatively savage. He makes crude jokes at the expense of others and then admonishes them for not taking it in good humour. He likes his shark steak underdone and rare. So it is possible for the white man to be more savage than the supposed savages who serve under him.
Melville uses the concept of savagery to come full circle and point out that for all are western trappings of civilisation, we are all savages and animals to boot, no better than the whales we hunt. This is best illustrated by a quote from chapter 65, The Whale as a Dish:
Go to the meat market of a Saturday night and see the crowds of live bipeds staring up at the long rows of dead quadrupeds. Does not that sight take a tooth out of the cannibal's jaw? Cannibals? Who is not a cannibal? I tell you it will be more tolerable for the Fejee that salted down a lean missionary in his cellar against a coming famine; it will be more tolerable for that provident Fejee, I say, in the day of judgement, than for thee, civilized and enlightened gourmand, who naliest geese to the ground and feistiest on their bloated livers in thy paté-de-foie-gras.
If westerners are content to torture geese to tickle their tastebuds, can they really claim to be any more civilized than a tribal African, or an angry whale?