Hi Chris, user styles should be able to help you out, I can point you to the CSS if you would like that.
Not saying this to dismiss your needs, I hope you don’t think of it that way! Everyone has different preferences and there’s no way we can satisfy everyone. If you’d like to tweak the interface, user styles (and custom CSS in the future) will be your best bet 
First you need to install the Stylish extension, which lets you apply custom CSS to specific websites. Link: https://chrome.google.com/webstore/detail/stylish-custom-themes-for/fjnbnpbmkenffdnngjfgmeleoegfcffe?hl=en
Then tweak the CSS like shown here: Customize Color Labels (w/ Stylish)
The background color hex controls the color.
I hope that helps!