lpalmaro pointed out that when the user scrolls up and down in fullscreen mode, the flicker of the background colors in the background, when the flicker shows up behind text like the location bar title, it could cause contrast issues for users who are visually impaired.

I'm not sure how strong those colors get; it depends on the background color of the webpage. Can you try this out and make sure it still meets the minimum contrast ratio needed for text?

If it doesn't look like the background colors can cause much of an issue given their muted palette, we can close out this bug.