Gallery images B&W to colour on hover

I'm using the Newspaper template and trying to create a black and white to colour rollover on the gallery section of my site (https://icosahedron-polygon-kjsw.squarespace.com/) pw: hello

I have tried adding it to the CSS but I think I am missing the correct section ID 

I am new to squarespace and cannot figure this out please help!

Please see the following.

Check out Heather Tovey's most excellent looking Squarespace ID Finder to get the collection id for your page. Once you have that, replace the collection id in the code with your own.

Let us know how it goes.