I did mine with Royal Blue. What I did was, I put water into a 2-liter soda bottle up to the bottom of the label. I squeezed the bottle and put the cap on, heated it up in the microwave until it got to between 120-130 degrees. I then poured in a bit of the powdered RIT dye, not even an eight of the package, maybe less. Shook it up after closing the cap. The water looked almost black, but the bubbles showed the blue. I cut the bottle open, and started dipping the cover in.
I had tried doing a gradient, but it didn't look too great, so I ended up putting the cover back in the other way to make it match.
It came out a purplish blue. It looks AWESOME! Will post pictures later.
I had it in there for a total of about 20 minutes to get this color. A six minute dip made it not dark enough to look stock, which is why I gave up on the gradient. Well, actually it looked stock - in comparison to the crappy color the stock one came.
Edit: See Post #611 later on here pictures & #618 for more details on how I did it.