ok, if I remember correctly (as much as that's possible) then there are two kinds of eggs, blue and white. These may or may not get "painted" over by brown. A white egg with lots of brown paint is a wellsummer egg, a blue egg with lots of brown paint is olive.
Your rooster likely inherited several brown paint genes (there are at least 13) from his wellsummer parent. If his ameraucana parent is pure bred and not actually an Easter egger he got one white shell and one blue shell gene and you'll get more olive eggers. If he got two white shell genes you'll get more brown or tinted egg layers. His offspring will probably still lay a range of colors from light green to olive to tinted eggs and even dark brown eggs. The only color you probably won't see in his offspring is pure blue since he probably carries too many brown paint genes to eliminate even you tried really hard.
You can improve your chances of olive eggers by using the hens in your flock who already lay light green eggs, if you have any.
For the wellsummer hen cross, if the roosters parent was pure ameraucana and not a misrepresented Easter egger you should get about half brown and half olive egg layers.
