Colours
========
Five colours, with four shades each, are available to build the interface.
The colour should be given, as a string, to the `col` argument of a widget
function.


.. code::

            red1    blue1    green1    purple1    orange1 

            red2    blue2    green2    purple2    orange2 

            red3    blue3    green3    purple3    orange3 

            red4    blue4    green4    purple4    orange4

