All clown fish are sexually immature, non gender specific. One clown will become dominate and that clown will turn into a female, the next subservient clown will be the male, all others in the group remain sexually immature. If the dominate female dies the male in the grouping becomes the dominate female, one of the non gender specific clowns becomes the male. It's extremely rare for a female to ever become a male again, it basically only goes one direction.
All clowns male and female exhibit a darkening or more prominent coloration as they mature. A lone clown becomes a female, so your clown is a female.