Why do you refer to some color mutations as “split” ?

A Green Split Blue Parrotlet - Why do you refer to some color mutations as “split”. What does "Split" mean? The term "Split" means that the Parrotlet is visually green, but it has the gene of a color mutation. So Green "split to blue" is visually green but has a green gene and a blue gene. When bred with a blue Parrotlet (having 2 blue genes), half of the offspring will be blue (a blue gene from the split to blue parent and a blue gene from the blue parent), the other half will be visually green split to blue (a green gene from the split to blue parent and a blue gene from the blue parent). Thus the color mutations are recessive, requiring both genes to be that color for the Parrotlet to have that color visually. The 3 Parrotlet Photos (below) are of the Blue Parrotlet Mutation. All 3 Blue's are Female Pacific Parrotlets. Just by looking at the different pictures-one would assume they are just "Blue Parrotlets" 

   

  Blue Pacific Parrotlet (F)

Blue Split Yellow Pacific Parrotlet (F)

Blue Split Fallow Pacific Parrotlet (F)