We ran a GoToMeeting last week with breakout rooms (great feature!). We had wanted to message everyone in the breakout rooms however the chat font was white on a light blue background. Any messages sent to the groups as a whole were completely impossible to read. The GoTo team tried to help to change colours, but this is not an option in the program.
The colours to individuals or all in the main room were great (black on green or pink).
Having white on a coloured background, especially a light colour, is not accessible to people, especially those with any accommodation needs. We strongly recommend giving the users the ability to change colours or that your colour choices meet accessibility challenges.