layer/block list selection background color

I removed the layer / block list selection background color option,
because you can set that with a style-sheet now;
actually, you can manipulate all aspects:

QTableView
{
        selection-background-color: #ccffcc;
        selection-color: Blue;
        font-size: 16px;
        font-family: "Arial";
}

Simply save that as arbitrary.txt and choose it in Widget Options.

https://github.com/LibreCAD/LibreCAD/wiki/Style-Sheets

Get hex codes:
https://duckduckgo.com/?q=color+picker&ia=colorpicker
http://rapidtables.com/web/color/Web_Color.htm