[sdiy] Bicolor LED driver?

[Luís Marka]

Hi gang,
I decided to use bicolor LEDs to indicate output voltage in a few 
modules (LFOs, for example). The idea is to have the red LED going ON 
for positive signals, and the green one for negative. So far I am 
driving the red half of the LED with a standard NPN transistor buffer, 
and the green half via an inverter operational amplifier at unitary gain 
followed by an identical buffer. The LED is a 3-pin, with a common catode.
Question: Is there a simpler way to do that? It would be great if I 
could get rid of the op. amp, this would save quite some space on the 
boards and simplify the layout, especially when I drive several LEDs in 
one module!

Best,
Luis Marka