There are two great general sources for Gray codes on combinatorial objects you might enjoy:
1) Frank Ruskey's "Combinatorial Generation" book.: http://tinyurl.com/yly4pq7
2) Don Knuth's "Art of Computer ProgrammingProgramming", Vol. 4, Fascicle 2-4 (published separately - all excellent). , see http://www-cs-faculty.stanford.edu/~uno/taocp.html
Preliminary versions of some of these can be downloaded from the internet archive.: http://tinyurl.com/yfo57t4

