I've seen this diode puzzle all over the net. No one has provided an answer. The curiosity is killing me.
My guess is LP1 LP2 LP3 for the image on the left and LP3 LP4 from the image on the right.
btw, electronics noob here.

 

Given no other information, I think those are the only ones that could be on.

 

that would be correct

 

In the left hand circuit, LP1 would be on at full brilliance, and LP2 + LP3 on at reduced brilliance.

I the right hand circuit LP3 and LP4 would be on at reduced brilliance.

 

This question is actually on the GROL license exam.