In Ron's circuit, it will work but you can use an LM393 if you don't want to waste half a comparator. Ron only used an LM339 because Multisim doesn't have an LM393, I had to do the same thing. I ran Ron's circuit and it did work, but I would add a little hysteresis to the comparators. I made a window comparator circuit to work with the display. I have attached the circuits below, and it has an example of 1V above, 1V below, and at 15V. If it is connected to the display, then it will be Red if it is below 15V, Green if it is at 15V, and Blue if it is above 15V.