Nice DIY project Peter.
On daylight dives I used to snap blue gels into the front of my Light & Motion halogen heads. That worked well because they had a slight recess that was just right.
I'm thinking of making some cylindrical cups to go over my Keldan Luna 4X lights to do this. I might have to get them 3D printed unless I can find pipe that has the right diameter. Failing that, I may copy your idea.
Kind of ironic. Get lights with a nice high CRI and then completely knacker it with a bit of coloured plastic over the front
The other strategy is just to throw so much artificial light on the subject that the ambient daylight is overcome, but that's not always conducive to keeping the subject happy.