I just took some pics...and make a collage of one Phänotype from my Poecilia obscura:
Just poor quality pictures, but enough for show the pattern - of this Morphe. All these fish are in neutral mood.
The differences are only in the upper part of the caudal fin. There are more or less little dots. Another similar phenotype shows the same pattern. Even the extention of dots. But the yellow oval in the caudal fin of the second phenotype is simply white.
The white and yellow phenotype can switch during their courtship behaviour into a brown - black caudal oval. Look here: