I find it interesting how different colors will affect different people in different ways. Of course, we all have our favorite color, but that does not always work in a teaching environment. Normally when I use markers to demonstrate a point, I usually use dark colors (i.e. black or blue) since the board I use is white and I've noticed that lighter colors, though they may help stimulate some students, do not work on a white surface and it may increase agitation and confusion for the students. I however will split between black and blue during different times to either distinguish or emphasize certain issues which may be important for the students.