Found this on Crutchfield.com. Included are both the diagram of the harness plug, as well as the color-coding associated with each wire in the harness.
Also, I read multiple posts on the forum that the Mazda3 and Mazda5 wiring is different. Well according to this, that's half true... while the color-coding of the wires is COMPLETELY different, the harness plug has the same layout of connections.
(I've also attached this document as a Word document for text and easier printing.)