Does anyone have flag color preferences?
Back on topic, I prefer the red/short, white, blue/long system, but that only covers things when greens are 30 yards in depth or so. When you get up to 45/50 yard depth of greens, I think a checkered blue/black and checkered red/black should be used as well.
Let's see... on a 30-yard-deep green, if red/white/blue cover 2-10/11-19/20-28, then we're talking about 10 yards per colour change. If we add the extra colours, a 50 yard green becomes 2-10/11-20/21-29/30-39/40-48. So the red and blue are still a 10-yard adjustment to your distance-to-the-center, while the checkered ones are about 18/19 yards, that is each flag colour change can be thought of as a 9 yard adjustment.
So, this system offers simplicity and consistency. You don't need to know how deep the green is in order to allow for 9 yards when you see a red flag. For casual play, this should speed up play by a few seconds.