Coloring your artwork is easy, anywhere, anytime with the no-mess, dye-based, KoiÂ® Coloring Brush pens! These pens perform similar to an artist brush. Make fine, medium or bold brush strokes just by changing the amount of pressure to the nib. The durable tip will quickly spring back to its original shape! The odorless, water-based solvent facilitates smooth blending and layering of colors.