He looks like a yellow face version of one of my budgies so I would guess;
Full body grey yellowface type two?
Full body, this is great !! Never thought of it. Does his cheek patches match a full body description ? Greywing, clearwing and full body amazes me to identify the mutation. Hope Guthwulf or Nev90 can give more insight to these 3 mutations.
Well from my understanding what would make him a full body grey is the fact that his markings are grey but the body colour is not washed out.
Heres a quote from what I was looking at
In addition to a dark factor, budgies may also have a degree of dilution. There are four types of dilution: greywing, full-body-color greywing, clearwing, and dilute. Greywing budgies have grey markings on head and wings instead of black, and the body feather color is about 50% diluted (washed out). Full-body-color greywing budgies have the same grey markings of the greywing but the body color is brightened (not lightened or diluted). Clearwing budgies have very light or no markings on head and wings and the body color is brightened (not lightened or diluted). Dilute budgies are washed out all over. The head and wing markings are very light, and the body color is about 80% diluted (washed out). Without any dilution, the budgie looks like the normal budgies seen above. "
He is a yellowface type two, and my guess would be either clearwing or full body colour greywing (one greywing one clearwing gene). He is definately not a greywing as his body colour and cheek patches are not diluted.
I dont breed dilute varieties, so Nev would be your man on this one.