bipolar LED across a switch to indicate off/on
The trouble with using power (lamp or LED),  well,  no matter how you do it, it's still power.  

Green LED is ON for when switch is OFF. Red LED is ON for when switch is ON.  

No matter how you switch the LED's (switch or transistors), those darn LED's still consume the same amount of power.  

Using transistors to switch the LED's on and off actually consumes a tiny bit more power.