In Ubuntu I installed 'GNOME Color Manager'. According to Ubuntu this software is supposed to be used with 'GNOME Control Center'. But I can't find 'GNOME Control Center' anywhere. Has it ceased to exist? My real problem is that I want to color calibrate my HP printer. But to do that, I need to print out a color calibration sheet without any profile enabled and later I need to import and enable a newly created ICC profile. According to the printer calibration service, printing of the sheet, without any ICC profile enabled, can be done with GIMP. But that seems like 'shooting sparrows with cannons'...
Not sure what do you mean, if you mean "gnome tweaks" use this command
sudo apt install gnome-tweak-tool
otherwise, i guess you mean the default control center of the system itself, that's gnome control center
sudo apt install gnome-control-center