chipboard question.

[kickasphalt.livejournal.com]

hello, all.
been lurking awhile, but this is my first post.
i have a piece of chipboard which i want to paint with acrylics. it's fairly light (like the color of raw pine), and i want the paint to gradate from red to pale pink. do you think i need to prime it with gesso, or should it be okay as is?

thanks!