grey is a combination of blue and greygreen mutation
cobalt is a combination of blue and darkgreen muatation
blue mutation is autosomal recessive - it means that two blue parrots always will get blue kids. Green parrots of blue and green parrots still will have the blue gen (just not visible) and such birds after crossing with a blue parrot, their kids have 50-50 chance of being blue. Two green birds with the blue gen have 25% chance for the blue kid.
Greygreen is autosomal dominant - it means that one gen is enough to be greygreen (or grey when the bird is "blue"). Also, I think it's impossible to tell visually if its sf (single factor) or df (double factor) - so when you cross a grey with non-grey, you either may got all grey(green) kids (if grey parent is df) or chances will be 50-50 (if the parent grey was sf). While crossing two grey(green)s, there's high possibility that all kids will be grey(green) (only if both parents would be sf, then it would be 75% chance of the grey factor)
Dark factor is autosomal incomplete dominant - the rules are similar as grey factor but one difference - you can see difference between df and sf - sf is called as darkgreen and df as olive (in the combination with blue: sf - cobalt; df - mauve).
There's an online mutation calculator but IMO it's very hard to use when you don't know genetic basics - so I hope this what I wrote above somehow helps. The link:
http://www.gencalc.com/gen/eng_genc.php?sp=0ParQua
Notes:
- "1.0" means male and "0.1" is female
- "grey" means the grey factor mutation, not the combination with blue (witch actually looks grey) - so for the actual "grey" you would have to mark "grey" and "blue"
