STABILO Aquacolor Colored Pencils ARTY pencil case, 36 pcs. The core of the pencil is 2.8 mm. The aquacolor watercolor pencils can be used on wet and dry paper or cardboard. If you use dry paper you can mix the colors together using water and a brush. If you draw directly on wet paper, the colors will automatically blend into each other. You can also apply the color to paper by running a wet brush along the tip of the pencil and then applying it to the paper.