@Djone ...
Thanks for sharing that video. I'm not much of a coder, and it would be difficult to know exactly what is causing those issues just by watching your video. Have you dived into the HTML to see if there is anything that would be causing things to change colors like that? Is there any "rogue" HTML code that doesn't need to be there? I'm not sure how your pages were designed, but it looks like a lot of work was done to make those pages look pretty nice. I don't know if this would be helpful or not, but you could try running the page through a HTML cleaner site to reduce some "rogue" code. HTML Cleanup
You might try by creating a new unpublished page in your course and then pasting in the cleaned up code to that page to see what it looks like compared to your original page...just so you aren't messing up anything in your current page. (Or, if you had a sandbox course in Canvas, you could do all that testing in there, too.)
Just a thought if you wanted to maybe give this a try.