I have never had the need too use more than one colour  using the invisible fluoro paint, however if the Glow paint is the same & goes on as a translucent, I would imagine colour separation is needed, although you could experiment with palette mixing.
When you paint with the translucent type, use a blacklight fitting to assist visibly, while applying it.
Also depending on wether you are using the black light fluoro tubes or UV cannons [floods] for the effect. This will also dictate the level of the stage lighting state that can be used effectively. Remembering that the fluoro tubes give 360 degree light, while the UV cannons are more directional.
With the fluoro tubes use an electronic starter rather than a normal flicker striking one.
Also if you use Lee 181 Congo Blue colour gels in the general lighting state, this will assist the coverage, when turning on the blacklight & dimming out the general coverage. Smoothing out the snap on of the blacklight.
Ensure you blacklight tubes which are in the UVA 315-345nm [longest wavelength]. The danger area is 280-315nm UVB. Shorter wavelengths fall into the UVC area  which is used to sterilise.