Great stuff, right from the cover onwards.
To honour the ruby anniversary, the logo and the red bits of King Carlos' cover have a plasticy sheen to them. I'm guessing the David Aja variant cover will have the same effect (being mostly black and white except for the red bits on Dredd's helmet)?
T.M.O tells us that all the stories in this special are ruby or red-themed, which leads to a bit of fun waiting for the red to appear (some a little quicker than others).
Into the special itself, and we've got six stories with one page interludes by various artists, just as in Prog 2000. The first interlude is a nice series of widescreen black and white panels from Jock, depicting a party attended by Dreddworld characters, which leads us to the Dredd tale, Blood. Fairly standard six-page one-and-done, though has a not-exactly judicial ending...
Rufus Dayglo draws a variety of early 2000AD characters to lead in to a M.A.C.H.1 / Zombo pastiche where the red theme is from Z.O.M.B.O's partner, Tarquin Ruby.
Mark Sexton draws an S.M.S. inspired Mek-Quake (that's what I think, anyway) playing with 2000AD figurines. I'm thinking of Wash's voice here: "Curse your sudden but inevitable betrayal!"
This leads in to a nice one-off Ro-Busters story, set in the Starlord / 2000AD and Starlord era where we find out the secret of a well-behaved Ro-Jaws! Hammerstein's eye glows red when he's angry, and Mr Ten Percent's when he's stressed - the only colour in the six pages. Over the page Cliff Robinson and Dylan Teague give us a centrespread (which isn't quite in the centre pages) of the Terrameks (and Charlie, and Mek-Quake).
Patrick Goddard takes us to the Doghouse where we're led in to a Durham Red tale (though Alpha features in almost as many panels as Red). There's a character called Red, there's space vampires and lots of blood as Lauren Beukes and Dale Halvorsen turn in a pretty good story. Carlos' Durham seems to look quite a bit like Integra Fairbrook in this seven-pager.
Bryan Talbot provides a full-page portrait of Torque for his interlude.
Mills returns for a second story with the tale of how Sláine tried to get in to the Red Branch. Ties in slightly to the themes that have appeared in the most recent book to appear in the prog, but largely self-contained. As well as the Red in the title, there's quite a bit of the red juice too, though not how you'd normally expect in a Sláine tale.
Cyber-Matt makes a brave attempt to stick up for the droids who have made 2000AD great over the past 40 years, before being found out by green bonce (this inerlude is from Mike Collins).
Rounding out the special is a Nikolai Dante flashback where Romanov red meets the Faberge Ruby. A few (non Danteworld) 2000AD characters appear in the first couple of pages but presumably only as fancy dress-wearing partygoers. Almost a pity, as the Dredd costume looked to have an interesting Imperial Eagle shoulder pad... A third source of thematic redness appears later in the tale...