If you are not going to show us the actual page or code we can’t really help.
Use the dev tools and inspect the page. You can see what element has the color and where the styles are coming from.
All we can do at this point is speculate which isn’t very helpful.
Clearly, something has that color as colors do not appear magically on their own. It looks like a bottom margin on the copyright text is collapsing the containers and pushing the page content up revealing the underlying element. Whatever element that is, it might be a container or it might be the body or html element.
As an example
If it only happens as the page is loading it may be some styles loading in initially which then is overwritten by styles loaded later. For example styles inside a <style> element might be loading first and then after all the CSS files are downloaded and the styles get applied they overwrite the style element styles.