Can I change the color of the volume indicator?
Is it possible?
If your talking about the drop down toggle on/off indicator color, then yes. Use the power control settings app.
But I think you are talking about the actual volume level color bar, and that is buried in the framework and must be modded on a pc and the flashed or pushed back to the phone. Out of all the themes I have done, ironically I have never changed that. So I will have to look into it later tonight or tomorrow for ya.