Why are some fish brightly colored?

In nature, most males are the colorful one and the females are not as colorful. (not as pretty) Why? Because the males want to attract the females and mate. If you look at a peacock the ones with the "eye" feathers are the male (the blue ones) the brown non-colorful ones are the female peacocks. So my guess is that the colorful fish are the males and the non-colorful ones are females. But don't take my advice, I don't know I'm right! it's just a guess!

I hope it helped (even though it was a guess!