brown | gray or blue | red or orange | green or yellow | black or white
About colour - remember that lighting is important. A bird viewed at a distance or in poor light will seem browner than it really is. At sunrise or sunset, the white parts of birds can appear orange, yellow or even red. Birds backlit against the sky or sun look blacker than normal. And we all interpret colours a bit differently. So some birds are listed in several colour categories to help you. Colour is fascinating - have you heard of structural colour?
2. Beak shape
3. Bird Size
Sparrow size or smaller | Robin size | Blue Jay size | Crow size or bigger