Edit Shopify Gallery to Only Show Variant Images

I need the product thumbnails to only show images that are related to the selected variant colour.

The plan is to relate them to the variant colour via Alt tag so that if I select "Blue" it will only show product gallery images that contain the Alt Tag "Blue".

There are various links online that do this such as https://gist.github.com/carolineschnapp/d3c1af82b915e9cae82929e6486f22fe

but these instructions do not work as my theme seems slightly more complicated. It is the Wookie Theme.