The three assault divisions (3, 50 and 3 Canadian) were prioritised for the Mk III helmet, along with some other stuff such as 44 Pattern webbing. Other units and formations were largely equipped with Mk II helmets, though the Mk III became increasingly common.
Canadian-manufactured Battledress has a touch more green, though the difference is very marginal and it still looks like cowshit brown, tbh. British troops were also occasionally issued with Canadian-manufactured uniform, so I wouldn't get too hung up about it.