It indicates -V/0V/+V. It is like my last circuit(Voltage direction indicator), but it's more simpler and it has a minimum .7 volts instead of 1.2 volts.
BLUE LED------------------ + VOLTAGE (+1.2V<)
BLACK LED(NONE)---- 0 VOLTAGE (0V-1.2V)
RED LED-------------------- - VOLTAGE (-1.2V>)
