When you're building a layout for prototypical operations, you have to make it easy for your operators to see where the trains will go as they traverse the switches in your track. This can be done on a control panel through colored lights, but what if you don't use control panels or want to keep the operators' eyes on the layout? You could install the colored lights between the rails (like we did on the Wisconsin Central project layout for Model Railroader a decade ago), but to keep things simple, why not make a marking on the ground throws? A quick dab of green paint for the "normal" mainline route and red paint for the diverging route quickly conveys the turnout position. If you use bright colors for the indicator paint, yard operators can sight down the yard ladders to quickly see which track the ladder is lined to.