Use custom colours for verse tags
Original Launchpad bug 1730445: https://bugs.launchpad.net/openlp/+bug/1730445
Reported by: raoul-snyman (Raoul Snyman).
It would be nice to be able to add custom colours to the C1, V1, etc, so that you can see the colours on the side in the slide controller. This makes it slightly easier to differentiate between the different verse types.