Basic ternary circuit to light three LED’s?
Here is a 4-transistor + 3 diode solution. 

V2 +12 D1 on 10mA only

V2 -12 D2 on 10mA only

V2  0V D3 on 10mA only

V1 0V all off. 







simulate this circuit &ndash; Schematic created using CircuitLab

To minimize the current drawn would require another transistor to invert the drive to D3 rather than shunting it. 

There might be a simpler approach, this does not quite feel elegant enough. 



Edit:

Okay, using Jasen's idea of common-base input, the below gets rid of the diodes and still has 4 transistor (5 if you want to avoid the shunt) 







simulate this circuit