I don't know of any option that affects the way mates highlight in the graphics window. There are a couple of options that tell SW whether or not to highlight parts in the graphics window when you select them. You might try toggling them to see if it helps and if you can live without having parts highlight. They are both located in "Tools"/"Options"/"System Options"/"Display/Selection". One is "Highlight all edges of features selected in graphics view", the other is "Dynamic highlight from graphics view".