Another type of VASI is the 4 light system.
4 red lights, 0 white lights: well bellow glide slope
3 red lights, 1 white light: below glide slope
2 red lights, 2 white lights1: on glide slope
1 red lights, 3 white lights: above glide slope
0 red lights, 4 white lights: well above glide slope
I believe I had a question on the above system.
As for the other type of VASI (with the red and white lights on top of each other), here's a good way to remember what's what:
red over red, you're dead (too low)
red over white, you're alright (on glide slope)
white over white, you're outta sight (too high)
Hehe...