Can’t Find Location of Code to Edit

I am in the process of fixing some accessibility issues on our website. One of the issues identified is that the green we use on hover over our course area tiles, is not high enough contrast.

However, I have looked in the style.css file, but I can’t seem to find where the colour controls are for this page – School Leaver Courses (knowsleycollege.ac.uk)

Any help will be much appreciated.

Thanks, Sam

The page I need help with: [log in to see the link]