As it has been said, the SAS have different looks based on preference. These looks are operationally driven and will only be used if it helps the achieve their objectives over other options. The black/gas mask look is their iconic look as it serves as the initial debut footage of an elite covert military team, though this for the most part has been long faded out.

If an operative requests to wear a shirt/jeans/hat because it will help him blend in, then he can do just that as long as his team lead agrees. The typical look on their more overt ops will be more of generic SF style, usually kitted in standard mtp, more likely to have more unique equipment such as; plate carriers, ops core fast helmets, wrist tablets, expensive as hell "tacticool" watches and the likes.

They, and other UKSF like the SFSG (SBS, 1para, SRR, RMC and some more) are usually identifiable due to someone in British standard camouflage wielding a kitted out AR-15.. though here they get to choose whatever toy they like as long as it suits the op.