Whiteness, at least from a racist perspective, isn't really about skin color, it's more like a club for 'approved' ethnicities. There's many Italians with darker skin than Mexicans, but Italians are considered 'white' and Mexicans are not. Same for large parts of the Middle East and Asia.

Romani are white skinned Europeans, but they're not 'racist approved', so they make up rumors they're actually from Egypt and omit them from the White Club.

The determination for what counts as white is highly inconsistent. Before the 1700s Germans were not considered white. Before the 1800s Irish were not considered white. For a time in the 1900s Finnish people were considered Asian (while many Finns were striking for better working conditions, what an odd coincidence). Italians weren't considered white until about a hundred years ago. It goes on and on.