Want to remove color blocks from page menu

Hello,
I want to remove the color blocks from the page menu - background, hover, parent, everything, and use an image instead. I have the background image displaying fine, however the color blocks are showing up over the image and removing the hex codes from the options doesn't work. I've tried using

background-color: none !important;

but that's not right, I'm thinking, cuz it ain't working

How can I go about this please? I'm not sure what file to edit in the editor, or if this can be done solely through CSS Inserts.

Thanks!!!