Color without an s can also be considered plural when used in a general sense. I like color is a more typical way to say it in American English than colors.
where is the plural indicated? isn't singular or plural ambiguous here
It is actually there in the word हैं at the end. If it was singular it would have been है. But, I didn't notice that little difference because the idea of saying colors was too far from my mind. We usually wouldn't say it like that in the US.