This is mostly about motorbikes but could apply to cars and others. A couple of local, I can only describe as idiots, think it's cool to have red lenses on their motorbike headlamps. My question is aren't there regulations/laws in this matter?

Probably, but widely ignored.

I hate the white tail lights seen on some vehicles. Not seen a red headlight yet, but it has to be incredibly dangerous for the user.

Idiot is the correct terminology