Using a couple stencils I’d already cut for the purposes of making baby onesies I stenciled the inside of the Ikea Vidja lamp to make a nursery lamp for baby’s room. I used the fabric paint I already had, but I think watercolor or colored ink might be pretty as it’s translucent. Acrylic paint, watered down just a bit, would work the same. The trick is to keep the stencil paint application light, using a dry brush, so the color comes through as well as the silhouette.
The stencil patterns can be downloaded from the project tutorial page here.