It's been played upon several times in the past... One reason being that Reimu's red, and Sanae's green. Reimu being the first miko, Sanae the second. Etc.
L is for Luigi, but I think that it's not actually versus Reimu (who is Red, the other miko, and the primary protagonist), but versus Marisa (who, simply, has the M). While it works better against Reimu, I think Kanako's line of thought was pairing with Marisa's M.
From what I gather, Suwako intended to make the S (S for Suwako) apron for herself, but Sanae misinterprets it as a gift and takes it, thus Suwako crying.
S is for Sanae who is a Sadist A is for Sanae Type A. N is for New playable character A is for Angst which Sakuya is having E is for Yokai Extermination!
