Comment # 3 on bug 70934 from Rafał Miłecki

Created attachment 88202 [details]
Colors OK on TV

In case of TV connected with HDMI a simple
xrandr --output HDMI-0 --off
xrandr --output HDMI-0 --auto
fixed the problem. There weren't any problems with colors after that. Even
gradients were OK (looks like TV is working in 24b mode). That white horizontal
stripes are result on my poor camera only.
Screen on this photo was perfect.