a lemon blue is a brown red with the blue gene. The best way to go about making them, is to breed a brown red to blues and take blue offspring and breed them back to a brown red again, in which you will produce the lemon blue.
Here's your answer from the genetic guru. And I've got Copper Black Marans (carries birchen gene?) Brabanters (cream gene)and blue and wheaten Ameraucanas and a brown red EE, so I am going to try this!
I love lemon blue too. But I couldn't find one of the few pictures I have seen of it.