Alternative term to 'Uncle Tom' for a black or colored person who is subservient to whites?
Solution 1:
The word "sellout" could be an option and can be applied to any race.
Solution 2:
I think anything that explicitly highlights the race will be considered too offensive or archaic in modern use. You didn't explain why you would want to use this term, but in today's society there's no need to point out that a black person is subservient to a white person unless you are trying to be critical in some way.
If you intend to make such criticism, but avoid being too offensive, use a phrase like "he's working for The Man".
Solution 3:
"House servant", Still on the plantation", “Shuck and jive” (the latter in reference to demeanor of such a person.