I only have German words for it: "Tauchlack" / "Glühbirnenlack" maybe "Dip paint" / "Bulb paint"?
This stuff can be purchased on amazon in germany. You can use it to color classical non colored light bulbs. So if you can get your hands on some clear bulbs, you could make blue ones that match your liking. These colors can also be mixed and/or diluted to have just the right color.
Conrad electronic sells some:
https://www.conrad.de/de/p/clou-tlk2...au-727571.html
For the LED option: the seller has concern because the power supply inside the led bulb has problems with fast on/off switching and may die in a short period of time. The actual leds inside the bulb are not harmed by the on/off switching. Also the response would be very different. The slow ramp up the real incandescent bulbs is hard to emulate. I would design a custom PCB that would emulate the response (dimming) of the leds and I would use just led emitter in the right color, maybe even with a little white added. So not just a bright blue led (>470nm) but also a (very dimm) cold white one for the blue channel. That would make it look convincing even with leds.