Guppy colors

[GoneFishing]

My guppies are a brilliant blue, and an electric red except their tailfin color is a lighter color and in patches. Could this be caused by stress? Or is there a nutrient specifically for color that they aren't getting? Any help would be greatly appreciated.

 

[Rosenweiss]

Is there any way you could put up a picture? Many guppies have various patterns on their tails that could make it look like they have less color.

 

[Khalix]

Also, do the patches appear to be actual color, or is any of it slightly "raised" or appear to have any abrasions? How long have you had them?

Only reason I ask is because one of the more common things I see at work with guppies is they will occasionally get shipped to us with a fungal infection that often seems to affect their tail fins first. At first it'll look like the color is just fading or something.

Hoping it's just a natural color issue.