The Rainbow CD-ROM is a collection of S/390 related software and hardware
technical bulletins from the ITSO and the Washington System Center.
The "kit" number is SK2T-2177, and sometimes is available also as a
feature when you get MVS, VM, VSE.

On MKTTOOLS there is a package called CDROMLST that lists all CD-ROMs.
Not sure if you can get to it via IBMLINK.

Cyndie Behrens
IBM - ITSO San Jose
cbehrens AT vnet.ibm DOT com