I flipped the color palette on the default XenForo theme and everything seemed to work fine. But when you try to add a link or insert media the text in the box is too light. I'm assuming it's using the light text but the box color is too bright. They wash out and you can't see anything.
It appears to be set as black. But when there is focus on the field it is yellow. If I click off of the field it goes to black. Not sure what is causing it to be yellow though, I don't see that any where in the css.
I have autofill turned off in Chrome. Happens in Chrome and Safari. In IE it stays black, though the cancel buttons are not styled.
Looks like it may have to do with -webkit-autofill ... even though autofill is turned off.
Admin CP -> Appearance -> Style Properties -> Forms -> Text Control, Focused State
Admin CP -> Appearance -> Style Properties -> Forms -> Textarea, Focused State
There are colors set as well as background images with gradients. I removed the gradients because they were yellow and I change the color to rgb(42,42,42) and it looks good for the inverted color palette.