If you use the Ecoline Brush Pen, there are also multiple ways to mix and blend colours using just the pens.
Creating transitions and gradients
To create a smooth transition between two colours, touch the tips of the penstogether for a few seconds, holding them upright. The fibre tip of the bottom pen will soak up the other colour temporarily so you can create a beautiful transition from the added colour to the colour of the original pen. The same thing can be done using the blender pen to seamlessly blend your colour into the paper and create a smooth gradient.
Mixing new colours
To mix an entirely custom colour, you can put the desired colours onto a non-absorbent surface (such as plastic) and use the blender pen to mix and apply your newly created colour. This also works with just one colour to blend your colour into the paper to create a gradient.