They could achieve the same effect by putting a number counting downward in each of the 3 spots, instead of just a plain light. So if the red lasts 20 seconds, green 15, and yellow 5, the light would show 20 counting down to 0 at the top in red, then 15 down to 0 at the bottom in green, then 5 down to 0 in the middle in yellow. As far as size/readability, it wouldn't be a big deal: those who can't read the numbers would still be able to see if it's a red, yellow or green, based and color and position.