There's also a pink for 1/2"- 2" waterlines and sprinklers, green for oxygen lines and grey for stainless steel pipes.
There’s also blue colored as well. Blue Monster brand.
I have some that's pale pearly gray. Not sure if they just cheaped out on a colorant or something, but it's definitely bargain-basement stuff so that wouldn't surprise me.
edit: Or maybe it's for stainless steel pipes?
Is there any particular reason?
Yellow is thicker and required by code to be yellow so it's visually distinguishable from the plumbing version.
From the packaging, it says it's more dense. The yellow color is used to indicate gas, so I suspect that's why they chose yellow.