I like dark themes, they are easy on the eyes especially north of the equator. When you reload any web page there is a brief white flash before the web page is drawn, can this be changed to a different color, e.g. dark gray? The white flash is distracting especially if you have a browser running on a second monitor, and blinding if on the primary monitor. I have tried various dark themes, as well as .CSS files, nothing makes a difference. It seems to be a default built in feature of Firefox version 62.0?