Change logo in new UI (Event Monitor)

They have used a variable in the CSS pointing to :root. You cannot overwrite this variable because it is also set inline at the html level.

So you have two options:

Option 1: Directly overwrite the CSS rule with a hardcoded image url

.headerLogoContainer {
	background-image: url("/assystimages/logo.png") !important;
}

Option 2: Overwrite the CSS rule to point to a custom variable in your own :root for reusability.

:root {
    --corporate-logo: url("/assystimages/company_logo.png");
}

.headerLogoContainer {
	background-image: var(--corporate-logo) !important;
}

Whichever you use, don't forget the !important to overwrite the any cascaded values inherited from the html in-line styling. I haven't managed to get it to work without this.