Hi Adriano,
Thanks for your message & js code.
It's almost working. When I first click the checkbox the button goes blue (I can change the color to #fec707 later) … but when the view reloads with the filter input the blue color disappears and goes back to the non-selected color.
You can see this on this page: http://nptravel.staging.wpengine(dot)com/country-page/usa/
Please replace (dot) with '.' for the link to work.
Hopefully this needs a slight tweak on the JS code?
Thanks so much for your help!
Nick