Rainbow pen is an ordinary pen, but has the mix of colors! Fill up your pen with red, yellow, pink and brown inks and you'll get the featured autograph in warm colors. Or add the cold colors such as blue, green, lemon, and grey and draw some sea picture. Also you can mix the colors as rainbow to mark your notes.

To create such pen you need to add each color by small portions in your pen one after another but without shaking them.