[Affected versions]: Fx 57.0b9 Fx 58.0a1 [Affected platforms]: Windows 10 x64 mac OS X 10.13 [Steps to reproduce]: 1. Launch Firefox. 2. Go to about:preferences and select "Colors.." from Language and Appearance. 3. Select the text color black and the background white. 4. From "Override the colors specified by the page with your selections above" "select Always". 5. Open a new tab. [Expected result]: The Onboarding Tour can be seen. [Actual result]: The Onboarding Tour is invisible. [Regression range]: This is not a regression. [Note]: a. Screen cast with the issue : https://imgur.com/a/5Lx5M b. Screen shot with the issue on mac OS: https://imgur.com/a/xYE7B b. about:support is affected as well. c. Not reproducible on Ubuntu: https://imgur.com/a/Pnc6N

STR 2: 1. Launch Firefox. 2. Go to about:preferences and select "Colors.." from Language and Appearance. 3. Select the text color black and the background white. 4. From "Override the colors specified by the page with your selections above" "select Always". 5. Go to about:support. [Expected result]: The page is properly displayed. [Actual result]: Some areas from the page are invisible. ( https://imgur.com/a/NIazF )

Is this related to high contrast mode? If not let's not worry about it.

The speech bubble still shows correctly in high contrast mode

Thanks. If that the case this bug should not block; we can't support every configuration where user purposely wants to break us.