Bob, the only thing I do is paint short lines. I tell the RD to look for a 2in x 6in white mark (or whatever color). At least around here nobody makes that kind of mark so it is actually very easy to identify. I leave it to the RD to write numbers or whatever at the marks if they want to. I don't like doing that.
The different colors are for situations where there are two overlapping course distances (5k, 10k) for the same event. A different color for the miles marks of each course.