Well that's the thing, possibly because of how it's running to HDMI via the OSSC the colors look great. It's just white that gets washed out. But I'll experiment with the RGB pots.
I use an ossc myself for testing miniguns and can confirm, every time, without fail, powering on for the first time without any adjustments results in too much "brightness"/intensity. The "default" positions fresh out the box have never been good on any of my builds, but heading to color bars and doing some quick tweaking always does the usual magic.