For the most part, they will stay like the hatch.
There's some little chance, and it does happen with animals starting out with the tiniest of black/coloured dots, that these dots will grow into nickel size, or even bigger. As a rule: I'd say that a Pied starting out as a 90% white animal... will stay like that, where there individual spotting/dotting, chances are that these will grow in size over time.
With Rosinante it's easy, She's got colour from Head to neck, and she got about 5mm colour on the very tip of her tail, followed by a (as of now) little spot containg around 5-6 scales, so: that will almost certainly stay, like it is.