You can set how you would like the area outside selection looks.

Each time you click icon, the display mode of outside selection switches.
You can directly select the mode by clicking [Selection] - [Show outside Border].

[Darken] is chosen here.

[Check] looks like this.

You can choose whichever you prefer. I myself do not use [Check]. It dazzles my eyes...

This is [Hide].

This is the best option if you do not want selection to disturb your other work, but you can easily forget about selection.
You will need caution when you use this option.