I've used regular Whisper White or Very Vanilla before as my base paper. It works fine and you need to be conscious to not use to much water.Tthe Water Color paper(used in yesterday's and today's cards) is speciffically made to work with water.
Click on the video below to see how to use Stampin' Write Markers and Aqua Painters to color your images!
Here's the Blog Hop List
Happy Crafting! ~ Dee