I bought the Dell S2419HGF and am trying to use it with my GTX 1060 (with the HDMI cable that was supplied). However, the colors are washed out and no amount of tinkering seems to fix it (especially the black isn't true black). When I test it, with the laptop not plugged in, then the colors are fine. I'm running the latest Nvidia drivers.
The S2719DGF is an AMD FreeSync monitor. To use 144Hz or overclocked 155Hz, you must be using a validated AMD FreeSync video card. Since you are using the non-validated Nvidia GTX 1060 video card, you must turn off Nvidia G-Sync (if turned on) and only use the S2719DGF AMD FreeSync monitor at native 2560x1440 60Hz. Do this, then check the colors. What GPU does the laptop use?