In PHPStorm, when you select a variable name in Javascript, it highlights all the other occurrences of that variable with a light background. How do you change the color of this background?
It's in Settings (Win/Linux) or Preferences (Mac) then
Editor/Colors & Fonts/General/Identifier under caret.
There you can set various options, like Foreground, Background, Error Stripe Mark and, probably what is of your interest the most, Effects.