Handling multiple colour formats

[mjwalter]

Currently, MEIMassaging only recognizes colors in the format #000000. However, the MEI guidelines allow for a number of formats, which may be used by the sibmei plugin.

The Python package colour supports multiple formats in a simple way, using a data structure that allows for equivalence checking, so that, for example, Color(rgb=(1, 0, 0)) == Color("#ff0000"). Unfortunately, this package is not included with Python installations.

Other means of recognizing different color formats – and making sure that different ways of representing the same color are treated as equivalent – would be welcome as well.