They still have colour - females will always have the orange/pink belly no matter what their mood or breeding status - but it certainly fades quite a bit after spawning. The intensity of my female lets me keep track of when I can expect babies. She's extremely colourful when ready to spawn, and as soon as her and her man do their thing, she's very pale. She stays pale for the next couple weeks as they raise their fry, and then she'll start to colour up again ready for the next round.
