Luminescent hands and hour markers.Automatic movement (23 jewels).Double folding safety clasp with divers extension (to fit over a wet suit).I have the Orange Monster myself, and its a great watch with a very robust feel. They have a reputation for being high-quality automatic watches sold at a reasonable price, and for having Omega De Ville Co Axial GMT unusually bright luminescent hands and hour markers. Hardlex is, well, harder, meaning it is less prone to cracking or shattering, but sapphire is far more scratch-resistant.
Seiko uses a material called Lumibrite which is very effective, especially on hands as wide as those found on the monster series.As far as I can tell, the primary differences between the new limited edition Blue Monster and the Orange, Yellow, and Black Monsters are: 1. The Blue Monster has a newer movement: the 7S36 rather than the 7S26. Both movements have the same features (quick-set day and date, no hacking, Omega De Ville Co Axial Chronograph and no manual winding), but the 7S36 has two more jewels, which leads me to believe its slightly more refined. 2. The Blue Monster has a domed sapphire crystal rather than the Hardlex crystal of the Orange, Yellow, and Black models.
Given the choice, Id probably go for the sapphire. 3. The Blue Monster will probably run you $100 to $200 more than its more pedestrian siblings.If youre interested in one of these, youll have to do some digging around the Internet to find one, or take a watch-buying trip to Japan. I would expect it to run you between $300 and $400 Omega De Ville Co Axial GMT.Update: I was recently informed that the Yellow Monster actually cant be grouped together with the Orange and Black Monsters. The Yellow Monster is a limited edition, as well, and also has a sapphire crystal, a slightly different movement, a cyclops over the date, and a couple other unique features. For details, check out this thread on TimeZone.