This change removed support for specifying custom colors to the Xserver:
Is there any other known way to define or extend color definitions
in the Xserver?
Stopped reading the rgb.txt file for specifying colors.
Have the clients choose the right color themselves?
Customizing the global color configuration for the X server was always a
poor fit for client color management - what do you do if different clients
have different needs? How do you ensure the changes are made on all X
servers your client may display on?
The use case is a common set of colors across many apps.
Default xcms.txt file shows the format.