The Color Computer Reference Manual
contains schematics and detailed hardware information.
See the CoCo Hardware Reference
on this site.
Spectral Associates (the people who made Madness and the Minotaur
) produced a series of
disassemblies of the CoCo ROMs! Here are those awesome PDFs:
Color Basic Unravelled
Extended Basic Unravelled
Disk Basic Unravelled
Super Extended Basic Unravelled