Here are a few of my favorite lady birds:
The female Red Crossbill isn't red at all. Her mate is a vibrant red while she is a muted grayish green.
The female Eastern Towhee is a bright bird, but her hood is a warm reddish brown while her mate's hood is deep black.
The female Downy Woodpecker is very similar to the male except that she has no red on the top of her head.
The female Ruby-throated Hummingbird doesn't have a ruby red throat at all.