Koi Colouring Brush Pen - Prussian Blue. Ideal for drawing, illustration, designing & sketching! These brush pens have a flexible brush tip with which you can simply draw lines of various thicknesses. The ink is water-based and enables wonderful colour gradations to be created. Pigma Micron is recommended for outlining before colouring with this item. Available in 48 colours & a blender, each sold separately.