I solved it! After a day and a half of screwing around with this problem, I found the answer. In the Nvidia control panel on the left side choose "adjust desktop color settings". Then on the right side under option 3. "apply the following enhancements", make sure "digital vibrance" is set to 50% and "hue" to 0%. My digital vibrance was set to 90% (did I do that? lol). A few percentage points below 50 and you see gray scale coming on, a few points above 50 and you see the oversaturated and garish happening.
I went wrong on this because option 2 on this window "choose how color is set" had "other applications control color settings" chosen, so I thought I had turned off all Nvidia intervention, but option 2 does not apply to option 3. Nvidia, apparently, ALWAYS applies option 3, regardless..