Changing colour about catify

[panikon]

You could use the element's style filter property, you can generate the correct parameters using this tool (to see the original code of the generator in stack overflow https://stackoverflow.com/a/43960991).

To do so find cat.style.backgroundRepeat = 'no-repeat'; and add below cat.style.filter = 'your filter';
E.g. to change the colour to #00a4d6 you'd put invert(70%) sepia(67%) saturate(6398%) hue-rotate(162deg) brightness(96%) contrast(101%)

Edit:
I made a commit in my fork with the change, if @yobert is interested I could make a pull request

[Fastidious]

That works perfectly, @panikon! Thank you so much!

[yobert]

I merged it. Y'all are way cool.