In Wavelab 9 Pro in all visiual metering, it is not possible to choose colors for Left or Right Signals.
You can only set them together as one color. I would lik eto make Left = RED and Right = Blue.
But that does not seem to be possible in any kind of metering.
For >2 channels, there could still be just two colours, used alternately to help guide the eye - a method that’s often used in forums, for instance, to separate posts visually.