Lemon is a line of "pastel" and is 100% compatible with all of the other "pastel" lines ... named or not.

Breeding a lemon pastel to a pastel gives each egg a 25% chance of being a super pastel, a 50% chance of being a pastel (either lemon or not, but you may not be able to tell the difference) and a 25% chance of being a normal.

For whatever it's worth, if you're spending the money with NERD, don't be afraid to pick up the phone and give them a call with your questions .... NERDs' customer service is awesome and you'll do a lot better than asking on a forum because they know better than anyone EXACTLY what you are buying!

-adam