Most neos have been selectively bred for colors. Because of this, there are rare true mutations. So, it is not as simple as a punnet square because of the many extra factors involved.
An example is your question about the rili gene. Some breeders have found it to be dominant, however all mine have been super recessive- to the point of not even f2 displaying it when crossed.
You are better off keeping a lookout for an interesting characteristic popping up in one of your tanks, and breeding for that.