No red channel? 4k AppleTV w/SEIKI SE39UY04

when i view as 1080p, looks great.

http://davecotter.com/screenshots/appletv/good.jpg

when i switch to 4k, there's no red channel (or it's insanely weak).

http://davecotter.com/screenshots/appletv/bad.jpg

i tried RGB vs YCbCr: RGB only works in 1080p mode, not in 4k mode

i'm using the recommended belkin high speed cable.

what gives? i was so excited :/