IntelliJ: How to auto-highlight variables like in Eclipse

File | Settings (Preferences on Mac) | Editor | General | Highlight usages of element at caret.

I think Intellij does not do this by default for a reason. If you click in a symbol on your code, you can hit Ctrl+Shift+F7, then it will highlight (High visible, not just like the default underline) all occurences of the symbol. Good thing is, if you move out the cursor of that symbol, it will keep it highlighted wherever you go.

Tip: You can highlight how many different symbols you want at the same time.
Tip 2: F3 / Shift + F3 goes to the next / previous occurence respectively.

Go into Settings->IDE Settings->Editor->Color and Fonts->General

Make a copy of Dracula to something like MyOwnDracula (can't change the built in schema).

Find whatever you need to change, in this case it's "Identifier under caret" and change the colors for foreground and background to your liking.

Even though this is a question on how to highlight all variables, point one and two will answer that meanwhile point 3 will make you more productive and rename all variables simultaneously if you so choose to do so.

1. With your cursor on an occurence.
2. Do Ctrl+Shift+F7 to select all other occurrences.
3. Then Shift + F6 to rename all occurences simultaneously.