Ooh right, you were talking about complementary colors! Sorry, I somehow missed that. @The Equestrian Zodiac
Yep, the part of the script that add new CSS was broken by the CSP.
Now, there are two ways to get around it. If you use Tampermonkey on Chrome, or use Violentmonkey on Chrome or Firefox, you can install this modified version of the script
If you use some other userscript managers or if the modified script doesn't work for you. You'll need to install browser extension to either modify or disable CSP for Derpibooru. For Firefox users you should follow Sollace's instructions here
in the 'additional note' section. For Chrome users, I recommend installing Disable Content-Security-Policy