I think this has been around for a while, but I didn't find any bug report of it.
In the "player colour" selection window the correct colour will only display when the zoom is at 1:1 for all players except the first when using custom colours. For all players except the first, when at a zoom level that is not 1:1, they will be shown the first player colours. It does not happen when using default colours, but once a new colour is selected, this bug will persist even if the default colour is selected again.
It's quite easy to check. Just switch to another player and change their colour. Now, leaving the player colour window open, change zoom levels and you will see the correct colour at only the 1:1 zoom level.
should be fixed with r5074. The bug must have been around for years :o