Umm, couple of things.
First, is it just me, or does that look more like carbon fiber? Plus wouldnt that make way more sense for a phone than Kevlar?
Any naturally colored Kevlar I have ever seen/use has been yellow. That doesn't mean you can't dye it. For this application Kevlar gets the job done and I'm betting was cheaper for the manufacture to buy. I wouldn't be surprised if DuPont subsidized it someone as Kevlar is actually a "name brand".