There are several ways to add white ink to colored card stock. In our recent class, we explored a couple of ways. Using a white pigment ink wash is a technique I introduced in a previous class. However, we touched on a few more, such as white jelly roll pen and chalk pen. The jelly roll pen provided the whitest application on the crumb cake card stock we were using. Here are two cards showing two of them. The smaller flowers were colored with alcohol Stampin’ Blends on the one card, and regular Stampin’ Write markers on the other.
Using white ink on colored card stock first, gives you the ability to add other colors on top. The white layer of color can be white pigment ink, white marker pens, like jelly roll or chalk, or even white color pencil.
This sample uses white pigment ink to color the flowers. 
This sample uses jelly roll pen to color the flowers
As an aside, and because she deserves credit for this card design, I want to mention that the idea for these cards was CASE’d from Judy Garza, whom I “met” after perusing her blog, during a late night email chat. It turns out we both use the same Web designer and hosting company, WebsbyAmy.
And I should also mention that this is my first post on my new site. I am still learning a lot about the many features of this new WordPress theme, but loving it all the while.