Okay here it is:
A green party light CAN AND WILL mess up your plants flowering cycle.
They are normal incandescents painted green. Some non-green light does escape.

They are fine for once in a while... but... I was an idiot once and left one on for 2 days about 2 weeks into flowering and man, did it slow the girls down.

As the Knowm says, go for the flourescents. They are designed with a much narrower wavelength range and will be much safer if you are forgetful like me and can't remember to turn a damn light off.