Second, it's hard to tell. It's like putting two mixed breed dogs together and asking what pure breed will the puppies be. Usually only way to tell is if you know the genetics of the fish, and the lines they comes from. But with pet store bettas, you could have two yellow Bettas and the babies could all turn out red. You really don't know. I am sure some would look like Mom and Dad but unsure of the actualy outcome would be.
I've never worked with reds but theoretically speaking you may end up with red, red with irid, cambodian like colors, green with red fins (if her green back ground is strong enough), and if you're lucky - orange/yellow (only 1 or 2)