I'm assuming it's a GSD x poodle? Because I've also seen that name used for Old English Sheepdog x poodle as well - a very different combo!
But yes, there's a lot of unknowns with mix, especially if it's a multi-generational cross (basically anything that's not pure GSD x pure poodle).
There's some colors that change with time (the fading/dilute gene in poodles that causes blues and silvers, for example, or creeping tan), but it's almost always a case of darker colors becoming lighter. Some breeds with ticking/roaning might develop it in spots that were previously white (like Lagotto Romagnolo), and Dalmatians are a wildcard with them developing spots due to an unusual form of the piebald gene, but no poodle colors act like that and I don't think any GSD colors do either, though I'm far from an expert. I'd guess that if pup's born white from that mix, they'll stay white.
You'll be able to know more about temperament by looking at the parents than the breeds in these cases. I'd guess that in general this mix would be highly intelligent and excited to train, and likely on the higher energy side. But on the flip side, both breeds have lines with an unfortunate tendency towards being high-strung and anxious, and I could see that being a really nasty combo. There's just too many factors to say where the pup will fall without knowing more about the parents and their lines specifically.
