Wait…the first code was lists /opacity and now you’re talking about links / color.
Also there is no parent/child relationship such as was required before.
Could you make a reduced case demo in Codepen. Hacking around using developer tools on a link is less than optimal.
As to where the code would go in a Tumblr template…I have no idea.
Oh…never mind…I see Nenad nailed it for you – http://stackoverflow.com/questions/36377379/hover-on-everything-but-aka-spotlight-effect-how-to-make-smooth-easy-hove