SAKURA-Koi: Coloring Brush Colorless Blenders. These flexible brush markers are special blender pens that create seamless washes and color gradations. Achieve fine, medium, or bold brush strokes simply by changing the nib pressure. The colorless water-based ink is transparent, blendable, and odorless. This package contains two Coloring Brush blender pens. Conforms to ASTM D4236. Imported.