Female birds are tough on this site and and in many guide books. You could always try a general web search engine for pix of females of different species. Sometimes that works, sometimes not so well.
However, working with the challenge presented can help improve birding skills. Most top level birders will tell you not to rely strictly on coloration for identification---that that can vary too much seasonally and with lighting effects. If we think of female birds as the same as male, just in "different colored clothes", then identification becomes about factors such as location, behavior, song/call, perching habit, silhouette, overall size, bill shape/size/color, etc. Sure there remain finer details such as those which distinguish between females within different groups (e.g., orioles), but at that point we'd be challenged even with complete photo guides.
Just my penny's worth of thoughts... jmm
8 days camping in Western Colorado and 5 new birds: Juniper Titmouse, Mountain Bluebird, Black-billed Magpie, Clark's Nutcracker, Gray Jay. Beautiful!!!