Is it ok to have painted crown moulding while we have natural baseboar

Certainly. I see this often on pbs programs.

If it's your home, of course it's okay! If you like it, it's okay. (BTW, it looks great painted or not!)

YES

My parents did this in their home, and I truly thought it would not look aesthetically pleasing, but it turned out awesome. They painted the crown moulding white and their ceilings are white, so I credit that for it working. If they had painted their crown moulding a different color, I don't think it would have looked right. Best of luck to you!

There is always rules to decorating but if this is your home and you like it. Look at others homes and use your own taste

Yes it is fine, and avoids the striped look which makes your walls look shorter. Usually crown moulding is the same colour as the ceiling.