Can I sub all or part of the water in WASC with blueberry pie filling to make blueberry cake? My daughter wants pink and purple cake. The pink is strawberry and I have a recipe for that but the purple is throwing me. I don't want to just add food dye to vanilla cake.

I would definately puree the blueberries and add more liquid to get it to a thinner consistency. You could also sub out some of the sour cream with the pie filling or blueberry yogurt.