Why is this wine different from all other wines?

Carmen reports her aunt served white wine at the family seder last night, so her table cloth wouldn't get stained while reciting the Biblical plagues - which involves dipping one's finger into the wine for each plague:

... This didn't sit well with most of us, as white wine doesn't taste very good with brisket and red wine shows up better on the plate.

"You can't do the plagues with white wine," one of my uncles said. "It's supposed to look like blood. You can't even SEE these plagues." ...