Hold the Mayo?

A snippet of an actual conversation I heard over lunch today:

Customer in sandwich shop: "What kind of mayonnaise is that?"
Sandwich shop worker: "White."

Really? They use white mayonnaise here? How exotic; I should eat here more often (haha).

Of course, if she had said it was any other color (i.e. yellow, green, etc.), I would've high-tailed it outta there and never come back...