Last weekend we wanted to watch some camera recordings on our TV, and I connected my Purism Librem 13 laptop via HDMI to our Samsung TV. The colors were washed out; it was no fun to watch.
It turns out that RGB colors can be transmitted in limited or full-range (RGB Full vs. RGB Limited). My intel graphics card automatically chose the limited RGB mode, causing the pale colors on the TV.
xrandr for the rescue:
$ xrandr --properties
HDMI-1 disconnected (normal left inverted right x axis y axis)
Content Protection: Undesired
supported: Undesired, Desired, Enabled
content type: No Data
supported: No Data, Graphics, Photo, Cinema, Game
aspect ratio: Automatic
supported: Automatic, 4:3, 16:9
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
link-status: Good
supported: Good, Bad
CONNECTOR_ID: 85
supported: 85
non-desktop: 0
range: (0, 1)
$ xrandr --output HDMI-1 --set "Broadcast RGB" Full
With that, the laptop did output full range colors and the videos looked good.