Are they interchangeable? Does sramd red /road=sram red cyclo?

There is no such thing as a cyclocross specific group.

A cyclocross bike will occasionally mix road and mountain groups (for example a Shimano road group with a Shimano Deore LX RD to allow for a wide range cassette...

Like Little Darwin said, rear derailleurs are chosen to match the range of the cassette. But shifters don't care what type of derailleur is there, as long as they match up how many gears there are.

Brakes are a different story. Road levers and MTB levers pull different amounts of cable, and so you'll have issues with the mechanical advantage against certain brakes as opposed to others.

Generally cyclocross bikes follow road groups. The most common deviations I see are mtb rear derailleurs & cassettes. One oddball set up is the V-brake on the current Tricross sport. Usually V-brakes are used with flat bar levers, but they put them on the Tricross to get rid of the shudder problem with the old cantilevers.

As stated there is no Cyclocross group but a mix. Look at the current Tricross Comp, it has almost all road 10 speed components and then Cantilever brakes instead of callipers.

The "cyclocross" crankset that came on my Novara Big Buzz was a Truvativ Elita 48/38. Neither road nor mountain.

Most Cyclocross hubs are 130mm which is road also. MTB's are usually 135mm.

-Roger

cyclocross groups probably drink more beer than road groups

I like beer.