bakeries often just use yellow food color
i'd keep some of those egg whites in there though
White Almond Sour Cream... its a cake a lot of people on this forum like to use. Check the recipes section for how to make it :)
Had to make a bunch of cupcakes asap, with no sour cream so I subbed in Vanilla yogurt, still came out nice and moist. Also used it for the chocolate with some mayo added and it to was nice and moist.
The *Original* WASC recipe does use whole eggs :)