Best way to do this is changing it in the correct sass file. In your theme folder there is a file called variables.scss, it has a variable called: $grid-bg-selected
By changing this you will change the selection color.
You can create a new scss file with new class defined and Add the new class name in the list view then import the same scss file in custom.scss file. Then compile the custom.scss file using koala complier.This will help you to achieve it
Is there not a quicker/easier way to do this through the properties->appearance->Class/Style of the list view?
For example, I can easily overwrite the color of the font in my list view by adding in the Style field: color: red; As can be seen in the attached figure. In my case, I want to overwrite the color of the selected object.