Those are coloured however.
I'm not sure but:
There's a chance that the chemical in the pickguards giving the glow was Strontium Aluminate.
CAS Number 12004-37-4
This is mixed into the plastic and then molded into a pickguard or anything really. Maybe some pickguard makers can try out this idea?
From Wikipedia: "Strontium aluminate is vastly superior phosphor than its predecessor, copper-activated zinc sulfide; it is about 10 times brighter, 10 times longer glowing, and 10 times more expensive than ZnS:Cu. It is frequently used in glow in the dark toys, where it displaces the cheaper but less efficient ZnS:Cu. However, the material has high hardness, causing abrasion to the machinery handling it; coating the particles with a suitable lubricant is usually used when strontium aluminate is added to plastics."
Warning: Using the CAS Number try to find MSDS (A chemical data sheet) before handling. Might be hazardous - However its used in child's plastic toys so it is unlikely. Safety first.
Or easier method to get some glow in the dark powder which can be easily found on the web.