Well, if you're a fan, it's can be as phabulous as your sense of esthetics. I've seen tacky RGB and very tastefully done lighting.
I looked it up on Amazon: 1 set of (2) LED strip lights goes for about 15 USD and up. So, that's generally affordable. But RGB can be incl. on just about any component, even your power supply. For a Corsair bronze 750 watt, I saw it add about 5 USD to the Amazon price, for eg.
Personally, I find it tacky in general. My PC's motherboard has an RGB controller, I shut it off in the BIOS. I have my Corsair RGB keyboard custom set, that's about all I will tolerate.
As far as fire hazard: ?? I doubt it would be strictly an RGB thing. If the power supply is over-loaded, it will almost always simply shut down. The PSU can be more of a hazard that way, than the RGB.
I have it on several components in my system because that’s what was available, but I leave it off a lot of the time because my side panel faces an outside wall so I don’t see it much. It is nice to easily tell if the system is on, and for some biased lighting. I’m indifferent, I care more about the performance.
Edit: Oh and it’s useful to make sure your fans are spinning on components if you have a glass panel and don’t want to open the case up to check.