I'm thinking of setting up an all-guppy planted tank and I was thinking of setting up a tank of just one variety of guppy - for example, just blue grass male and female guppies.

What I am curious about is whether when the guppies breed, the next generation will remain as blue grass or am I likely to find that although the parents look blue grass, the fry may have other colour genes in them? And, eventually, would my tank of blue grass guppies will become a tank of mixed colour guppies?

I want to know this because I don't want to spend a lot money on buying just one variety of guppy only to find that the end result will still be mixed guppies anyway. I might as well have spent the money on getting more mixed guppies rather than getting less single variety guppies.

Thanks.