I've noticed some leagues have different box colors and formats wondering the coding behind it?

look at the header coding.. You'll see sections for Portlets 1, 2 and 3.. in those sections you'll see hex coding for the colors.. they'll look something like #ffffff.. google hex color codes and find the color you want to change it to. There's prolly gonna be some trial and error on your part, so the best thing i can tell you is to copy your code in a word or google doc so you can always go back to it incase it messes up.

good answer