Tricky one I think. Depends on the context.
For instance, I married a red head. My family were predicting the gingerness of my kids whilst they were baking. All a bit of fun and no one meant to any harm by it.
If it's harmless speculating I don't really see an issue.
If it's along the lines of "I hope he's not too dark" then of course that's disgusting
Sounds a lot more than excitable guessing or harmless curiosity which is not on
