Colors

Something that would probably be the easiest is color genetics (what color the guppies are) because it is easy to observe. I don't know however though if there are complications with that or not....

Here is a website that I googled and it is a conversation about guppies and color genetics. I'm not sure how reliable this source is though.
http://www.fishforums.com/forum/livebearers/4036-guppy-colour-genetics.html
Here's what I got from it:

BODY COLORS
Recessive
gold/tiger/bronze
blond/gold
albino/wrea
lutino/wrea
cream
blau w/ red
blau
blau w/ yellow
white
silver

Dominant
grey

FORE BODY COLORS
mostly y-linked

Red
H/B reds are dominant. (H/B?)
When crossed with a gray female, 100% offspring should be red

Purple
Dominant!
When mixed with green, green becomes darker, not purple AND green, but a mix.


Albino (I have one of these)

White

Coral/Red

Gold

Leopard

Grey/Gray (?)

H/B Red

Blue (I have a bunch of these)

Pastel