If you are connecting from a DVI (or sometimes DP) port on your GPU Card--via an adapter cable--to an HDMI port on your monitor and the display looks magenta, you can fix the issue in the monitor control panel. Go to the monitor Color Settings; select Input Color Format; change from RGB to YPbPr. That should solve the problem.
Connect one 4k monitor to the DP port.
Connect one 4k monitor to HDMI port.
Connect two 4k monitors a Sonnet Thunderbolt 3 to Dual DP or Dual HDMI adapter connected to the Thunderbolt 3 port.