Same here. It takes 7 moves on the left side. Then in 9 moves you can have all diamonds lit, but when you finish changing remaining blocks to blue, you are out of position and have to spend one more to get back.
The trick is to turn the left-bottom light into blue first in as few steps as possible. It took me some time to figure out, and then I get from 18 to 17.
If you really want to know, I found someone who has posted solutions to every level and locations of everything. Tell me if you want me to tell you where to find it.
http://www.ps3trophies.org/forum/quel...