How to change $this color, colorscheme PhpStorm

I'd like to know why the color of $this in my PhpStorm isn't the one used by local variable. I've looked through every option of the "Language Defaults" section in the settings but i couldn't find it. Here is an exemple (I'm not allowed yet to post embed images x))

I'm using the color scheme vim Dark, and I like it but I want to customize it by changing this color, which is too dark.

Any Help we'll be greatly appreciated ! :)