"s o" wrote:
cylinder head's color is a little different(a little
duller, I guess) from the block. Is this the beginning of the end for
an engine?

I don't know but I wouldn't allow it to get extremely hot again. Pull
the thermostat and see if that helps. If it looks like it's gonna
overheat again, replace the impeller (or you might just go ahead and
do that now as well).

Rick