Possible Duplicate:
“User accounts” or “users account”
“BookList” or “booksList?”
Is it correct to say “lesson count” or “lessons count”?
should a list of tokens be called a “token list” or a “tokens list”
“Employee list” or “employees list”
"Thing count" or "things count"
And others

I know I can say

what color of towel do you like?

And the same:

what towel color do you like?

I also know I can say the same about multiple colors:

what colors of towels do you like?

But I'm not sure if I should say:

what towels colors do you like?


what towel colors do you like?