The easiest way to do this, without any added programming, is to modify the GI relay. Actually you probably don't even have to modify it. But when the GI relay pulls in, all the GI lighting goes off. But the relay is SPDT. Meaning that when the relay is pulled in, and it turns off the GI lights, you could have it light the UV. Either directly (depending on the UV voltage), or through another relay. It would be pretty easy to do. About 15 minutes of work.

You have bigger problems though. I have done exactly what you are doing (not on Time Fantasy, another game.) You are basing everything on that overhead black light. But in reality, that's a bad plan. you want the lights *inside* the game. I did a pin stadium type arrangement (and my game was more modern WPC style, with higher cabinet side walls, so the light is up higher). i could not get enough UV light to really light the PF. Your cab as very short side walls, barely enough room for a pin stadium type system. And the light won't project down on the playfield (more sideways). Maybe you can come up with another plan. But with the lights on the side, I just could not get enough UV. I tried UV tubes (they sell 24" tubes at 12 volts) *and* LED strips with the tubes. Just not enough UV light. I could never get it to glow like you show in the video, or even close to that. just not enough UV light.

Getting the lights to turn on at the right time is easy. Getting the PF to look good without having that big UV light overhead, that's a whole other plan...

Yea the overhead blacklight looks great, no doubt. but are you going to have a tripod over the game to use that light? probably not. i mean i guess you could, but it's clearly not ideal.

i would forget about the code for now. again, that's pretty easy compared to the issue with the light. because if you can't solve that problem, then code or no code, it does not matter!

speaking of paint, what UV paint did you use exactly? i used just water based acrylic paints from Michaels that are like $1 a bottle...

I looked up the wildfire UV paint man it is expensive. but what wildfire type did you use to mix with the craft paint? this may solve my problem...

that amazon link is for particular colors... i thought you were using a UV pigment, basically no color except UV pigment, and added it to $1 craft paint. Hence turning that craft paint color into a UV reactive color. Or am i mis-understanding this process?

I'm trying to understand the process here...
so you get the wildfire from the Amazon link above that you posted:
Deep Violet, Bright Orange, Bright Red, Hot Pink, Bright Green, Brilliant Yellow, Deep Yellow, Deep Blue, Magenta & Optical White
but these colors are not usable directly. So you mix them into cheap $1 acrylic colors?
i'm confused...

These relays are such high resistance, they won't be problematic. Look at the flipper relay. it's ON for the entire time the game is playing. sure it runs at 5volts... but look at gottlieb games. their 'game over' relay (30volts) is 'on' the entire length of the game, without issue.

they make glow in the dark balls. it looks like a twilight zone ceramic ball. but it's heavier. maybe try that.