Actually it isn’t possible, but this is on our internal wishlist.
You have asked for the color of the waveform in the Mix Editor after voicetracking here: Color Voicetrack in Mix editor
Well, the rules for waveforms in the Mix Editor have remain unchanged:
[MixEditor]
WaveformNormalColor=#FF0000
For the Voicetrack Window there are no settings but we will check if this is possible in the future.