Hi,
iMessages which is the new part that was added to iChat to make the Messages app can Text to Apple IDs and to iPhone Numbers (and those iPads with SIM Cards).
Basically it uses your Contacts (formerly the Address Book) list and your contacts email and iPhone Numbers.
If you are trying to contact a person by their Apple ID on their iPhone but their iPhone is not on WiFi or in contact with the cell/Mobile Service provider (Or Off) then Messages will turn the Name red.
It tends to be a standard message about the Name not being registered rather than quantifying it as Out of Contact (it could be it has been deleted from the iPhone).
To be clear.
The message is generic.
They may just be out of contact.
They may well have deleted the Apple ID from their iPhone.
10:31 PM Wednesday; October 3, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously