Thanks! The pattern is oddly hard to see; Rowling does a great job of disguising it with Snape's general surliness and nastiness, but, once you do notice it, it's really striking. I don't know if you read Sionna Raven's comments, which I'd linked to earlier; she pointed out that the Prince family motto translates as "to aid the unfortunate." And the colors are red and gold.

BTW, I am very impressed by your writing experiment, and have my fingers crossed for both "Knife" and "Touching Indigo".