From Left To Right- (1 Juvenile) Grey Green (No Dark Factors) Sf Spangle (2-3) Grey Green (1 Dark Factor) Normal (4-5) Grey Green (2 Dark Factors) Cinnamon

Why Is Grey Green Considered A Dominant Color Adding Factor? Grey green is a dominant color adding factor. The reasons for this is because it changes the normal green mutation all over the body, altering the color of the body, cheek patches, head/wing markings and tail.

Effect Of This Color Adding Factor On Body: Grey green budgies will be an even shade of light olive green (lighter than a dark factor olive green) depending on the dark factors the budgie has on their chest, breast and rump where it will be the darkest

Cheek Patches: Deep blue to silver grey 

Main Tail Feathers: Black

Dark Factors: Grey green budgies still have dark factors. For example a grey green budgie with 1 or 2 dark factors can be noticeably darker than a grey budgie with no dark factors.

Single Factor And Double Factor Forms: There is no visual difference between a sf grey green and a df grey green. If you are unsure of their  background the only way to know for sure is by breeding the bird in question to a normal (not grey) blue or green mate. If there are any normal blue or green chicks from this pairing the grey parent is a sf, as all the chicks would be grey with a df parent.