If that's the only thing in the battletech universe breaking your suspension of disbelief, considerer yourself lucky
It's far from the only thing. Lasers are really shitty weapons, due to some basic physics. If you've got relativistic particle beams there's no real point to lasers. It's just that lasers with visible beams and pew pew sounds are cool, while photomultiplier night vision isn't. Rule of Cool satisfied = disbelief is easy to suspend, because it's awesome.
I think that paint scheme can be very important Especially when considering Hero Mechs. Case in point... Yen Lo Wang: When I started piloting this mech I would get Alpha'd right off the bat. AC20 shot off, and then left alone. This happened repeatedly until I ended up removing the big blazing rising sun paint job from the mech by changing both colors to standard olive drab. First match after doing so... 4 Kills and 500+ damage. Ilya Muromets: Alpha'd untill I changed the paint job to standard black Firebrand: Same notation as above Jester: Alpha'd For some I think it may just be a "That guy is in a hero mech, he's dead" sort of thing, or a "look how bright and shiny.... He's dead" kind of situation. With the Yen Lo... it's obviously tactical. Making your mech easily recognizable (IE. HERO), or painting it up like a Fishing lure is going to get you noticed. If you are just that good, or plan on running through enemy lines as bait I suppose that is a good thing. Otherwise muted colors are probably best..... I have more thoughts on this, but work calls.
Agree with ski - if you want to be cool, paint your mech whatever you want, if you want to gain any possible (slight) benefit from colors, then you need to not draw attention. He picked green to look like a noob, I pick browns to help blend in as best as possible for tourm/caustic/rc/fc.