I don't know if it helps, i'm not experienced with circuit design, but i have done some work in the simulator for you.
I'm not sure, if it works in real world, but you could try it.
You can have following states (A=top switch,B=bottom switch,LED 2=top LED, 3=bottom LED):
!A&!B -> LED 1(most right one)
A&!B -> LED 2
!A&B -> LED 3
When you have A&B -> LED 2+3 are on both.
I hope it helps you at least a little to get a basic idea. Current is pulled away from the transistor base to switch off the LED you have no switch for left when the other transistors are on...
I have also tried this 4th state were you have no LED lighting.
This one i'm pretty sure is not a good solution, but at least in the simulator it works.
With A&B all LEDs are off.No, i've deleted that...it looked
.
You can download the simulator (google) and try yourself.
Have fun, Tom