I believe it is a yellow faced blue opaline clear wing.
To breed them your male must be split or visual opaline, mabey clear wing too but not sure. And either of the parents can be blue or yellow faced .
It is a combination variety, not an actual mutation per say. It is a combination of yellowface opaline clearwing blue series mutations. That is the official combination, although many people readily convince themselves an yellowface opaline spangle, or opaline greywing etc etc are 'rainbows'. It really doesnt matter and to be honest, obtaining the proper mix can be a long process if you do not have rainbow stock to start out with as you are dealing with recessive and dominant genes.
Here are photos of my two rainbows Diego and La fiesta. I'm planing on breeding them in the spring. Diego's mutation is opaline, yellow face type two, cobalt, clear wing, dominant pied. La fiesta's mutation is opaline, yellow face type two, sky blue, clearwing, clear flight. Both have a pied spot on the back of their heads.
To breed rainbows you will need your two birds to have or carry multiple mutations. So lets take it one mutation at a time. Opaline is a sex linked gene. That means your male will either have to be opaline or carry it. Yellow face type two is dominant. So at least one of your birds doesn't matter what one will need to be yellow face type two. Blue series is recessive. It would be easer to have two blue birds but you can have one blue bird as long as the other bird is carrying blue. Keep in mind that green is dominant over blue. Clear wing is recessive. You will either need two clear wing birds or one clear wing and one carrying clear wing. Good luck I hope that helps.