Nilsen, All channel is disabled in the MAs, except for Salutes. They are still sent automatically (.s ) on chan1 and thus can be read by all online.
Common channel for cross-country communication is channel 200 text (which displays also as grey BTW, but has a "200" in front). You can only read that channel when you actually have it tuned in one of your radios.
For a while, in the EWA/MWA All channel was enabled again, so some of the noobs might have talked on it. Im not sure if it got disabled again (but i hope so).
White text is private messages. Only the sender and receiver can see it. It can be used by tuning a text channel to someones gameID.
Private text (white) is also used to send the automated check6 call and collision messages.