Black is the traditional color for clergy; and these days white or grey for summer. Also Purple for Bishop, Red for Cardinal.
Other colors are regarded as a bit 'worldly' for someone who is supposed to be living less extravagantly.
Manufacturers have come up with other colors, (blue, green, brown, orange hawaiian etc.) but these are really sales 'gimmicks' (Like glass or pottery 'chalices' instead of metal) and not regarded as proper in Church Canonical tradition.
But various Protestant Clergy who do wear the collar rather than suit & tie, often wear these. They are very popular with some Afro-American churches.