Thanks the for the comments and feedback all!
Nice one for the "Guardsman of the 5th Arcadian Regiment" picture, I hadn't seen the full page version in years! The iconography was always a little confused. The guy in the picture if from hiveworld Arcadia - hence the Spiders gang tattoo. He is not from Necromunda yet his uniform is pretty close in colour scheme. I note in particular the helmet stripe colours are Green(assault), Yellow(command), Red(tactical) and Blue(support). I have gone with Green(support), Yellow(command), Red(assault) and Blue(tactical) as it seemed more suitable this way IMO.
In terms of weapons I plan to mix and match with whatever I have available that I think works rather than sticking to only using the classic RT era ones. My Necromunda is populated by a large number of crazy ass gang bangers who are happy to scavenge every gun they can for the "squad stash". Each squad will be painted in a manner that differentiates it from every other squad in the force - variations in uniform are not uncommon even between squads. This will hopefully afford me getting a sense of each squad being a mini-gang withing the greater gang of the platoon and so on up the command chain. The uniforms are to be more codex at the bottom (Whiteshields with classic lasguns and no gang markings), less so in the middle (tactical squads with mixed equipment and veteran/gang kill markings), and neater again with senior command squads.
@ aliensurfer - I am well aware of the war crimes of the Red Era but that won't stop me from abusing it on these guns.

Actually the red did cause me to pause for thought for a while. I think red is a great colour for wargames figures in general (redcoated Brittish infantry FTW) and usually try to get it on there somewhere. It works best on these models when it is not too bright, based off the GW scab red paint works nice enough. I like being able to eyeball a figure from across the table and easily tell what it is in a game and these guns will certainly allow that to happen.
Generally I would love to have a look at your converted or painted classic guardsmen if you can point me in the direction of images.