I have a graduation quilt to do also. But before that, I have a wedding in Jan. and one in Feb. (wedding cakes).
The question about the log cabin. I'm no expert, but I don't think it's whether the dark is on the top or the bottom as much as how the blocks are set to achieve different patterns on the quilt. A while back I had googled Log Cabin quilt blocks and one of the sites explained the patterns. I wish I could be more help.