You can goto the URL opera://flags/#enable-force-dark and try one of the flag's specific settings to see if one helps. Besides that, not sure, especially without having a link to the page in question and a description of what should be white that isn't.
you can try disabling chrome dark mode
you can verify if you have any dark mode extensions
you can also reset opera flags, enter this in the search bar : Opera:Flags / disable force dark mode
GL
Working fine as of this update this morning. This dev team needs to seriously address its processes for identifying and repairing bugs in new releases.
Interesting - turning acceleration on again and setting opengl as you suggest, the minimize / maximize fixes the icons moving / small rectangle drawing first problem.
However, the screen still appears empty for about half a second before it is re-drawn and in this regard is very similar to when acceleration is disabled.