Red Lunia 929 has subtle dark streaks on casing

[Jeffrey Brooks]

About a half inch from the right of the camera there is a very subtle dark streak- line the runs vertically and is about a half inch long. It isn't black or anything but just looks like a discoloration in the red. I exchanged one phone that had this, buy the new one has it in the exact same spot. I'm assuming it is an antenna or NFC plate or something on the inside of the casing but I'm not sure. It is visible almost all of the time except in certain times of lighting. Does anyone else notice this on their red one. I figure since I have had 2 that had it in the same spot it might just be all of the red ones. Its something most people would have to look for to notice.