🧪 PhpStorm Tips & Tricks #54 - Modified Line Colors
Whenever you modify your code, you can see a little color indicator on the side. When you click it, you even see the what has changed. (change list)
The used colors are defined by your theme. But like everything in PhpStorm, you can change those colors too. Check the preferences for "Color Scheme -> VCS" and "Color Scheme -> Diff & Merge".