My daughter's eyes change according to what she's wearing/ what colors are around her. If she's wearing green, she has bright-green eyes -- doesn't seem like they could be any other color. But if she's wearing gray, they're gray. They're sometimes more hazel. Sometimes a tiny bit blue.
If I look at them closely, they actually have a bunch of different colors within the iris -- they're not monochrome, at all. There isn't any actual green pigment but there are strands of bluish and goldish that next to each other, with the right background, look green.
Babies' eyes definitely change -- she was born with eyes that were a different color than they are now. But I don't think the intrinsic color changes on a short timescale, just how the color appears in context.