Overdriving lights etc

[BCOrchidGuy]

Does overdriving a fluorescent tube change the colour spectrum? I know that people OD the Radium bulb (HPS I think) with a Murcury Vapour (again I think) ballast and it changes the spectrum. If I remember right the Radium bulb is rated at 360 watts and it's a 430 watt ballast that is used on marine aquariums to make the light whiter or less blue.
What I'm thinking or asking is, if I use a workhorse ballast and run two 40watt NO fluorescents at 60 watts (1 actinic and one daylight) will there be a shift in spectrum?? If so does that occur as well with the Ice Caps when they underdrive the VHOs?
Will using a tar ballast give me different results?

Doug