By default local variables in IntelliJ are not colored in any way. As a result, the local variables are blended with the rest of the code and you have to make a little but present mental effort to identify them when reading the code.
The good news is that IntelliJ allows setting the color of local variables. Here is the snipped of the configuration screen:
The challenge is to come up with the coloring that would look natural and go with the rest of the coloring scheme. After trying to come up with a color that would fit into the already busy scheme, I have finalized on the "black bold" for local variables. It is not very intrusive and you still can spot the local variables easily: