Have you tried the Stampin' Up watercolour pencils? They are fabulous for colouring and they work amazingly on coloured cardstock!
This card was created with the Celebrate Sunflowers stamp set and I have used the watercolour pencils onto crumb cake cardstock. You can also see a hint of the Be Dazzling specialty paper which is a sale-a-bration offering.
The card layout is simple and really allows the gorgeous sunflower to shine!
To shop Stampin' Up products from my store CLICK HERE!!