This should probably be moved to General discussion.
To answer your question, there are no limits in that way anymore if you're plan isn't to port the game to an older platform. Like NES/SNES you would have to use the restrictions, but if you intend to have this on a modern computer/console You shouldn't have to think about colour restriction.
there are other reasons to not use too many colours. You can get better readability on smaller sprites etc.
Hope that answers your question
/coffee