Why the perk color changes on ptb?

I'm probably just dumb and it's listed in the ptb notes, but it just threw me off, that's all. Yellow is gone, green is the new yellow, and blue is the new green..? Okay.. but why not just change yellow to blue instead of swapping for green? Would that not have been a bit simpler? I mean I get in like, sense of ROYGBV it makes sense (GBV - Green, Blue, Violet) just seems.. a different color could have been picked if that was the thought process? Orange, maybe? Just to save the initial green items and keeping them as green. Hell, maybe it's for colorblind adjustments and I'm just being ignorant, but still.. why swap the green?

Idk. All thoughts about it aside, it's a pretty blue! I'm not mad at it, I'll adjust to the change if it goes live. Just.. odd choice to swap the green in place of yellow like that, to me.