Sorry if this is a common question (tried to search it and didn't come up with anything) but what is the significance of an otherwise normal-looking BP with a "clear belly" or "white belly"? Is it a genetic marker?

I ask because my new ball python seems to be normal, but she's got some very vivid markings/coloring, and I'm pretty sure she's got a white belly (though I'll have to check tonight and see)...