@pitaj
Not the icon, but the category header background.

Vanilla theme:

code_text
<div id="category-1" class="category-header category-header-image-cover" title="" style="
							
							background-color: #080382;
						" data-original-title="Announcements regarding our community">```


Using i.e. this does nothing:
.category-header .category-header-image-cover {
    background-color: transparent !important;
    }

In /admin/manage/categories/1 user can only choose between colors. If a drop-in option is too much of a work, there could be radio button called "Transparent" next to text "Background Color".

I can't express myself enough how frustrating it is trying to adjust the theme whilst Javascript is forcing layout via hardcoding it to the source.