Łukasz Gliński
I think AMT-11/AMT-12 (gray/gray) camo was introduced later on during the war and is mostly seen on Yaks-3/7/9 and Las-5/7/9/11.
Migs-3, Laggs-3 and Yaks-1 are often seen in the green/black-green camo.
For sure green/brown mode is completely fictional (in case of fighters).
I'm not specialized in the russian planes, so I recommend to look for more infos (e.g. here: airforce.ru/book_review/pilawskii/index.htm ).

P.S.: Just found it: sovietwarplanes.com/mig3/colors/colors.html

Stilicho
I'm quite sure I know a lot less. I do have the Pilawskii book but I gather it's out of favour. The kits I'm posting now are at the end of my list. Ones where a.(like this) the box art differs from the instructions inside or b.(like this) I can't understand them anyway. I did have some quick looks through the Internet for more recent opinion and I can remember one which did favour the 2 greys . As I recall this particular aircraft is supposed to be one of the last LAGG-3s built. Yes,I agree it's an early appearance of the late-war camouflage. I did this one after the Toko kit which is also ex-Dakoplast and the two Greys scheme is there on their 66 series kit. I'm quite happy to be shown to be wrong, but I did check and I'm not making it up. You can always change it. You should see the ones I have left which include a purple Jaguar and a Metallic black Ki-100. Thanks for the link, will check it out after dinner. 7.45 P.M. here.