Good info, MacLowlife! Thanks.

I also believe I read that the scalloping and the black color refer to an incident of burning, though I can't remember now what was burned.
Hmm, the only incident I can think of that would involve burning (or be important enough to warrant reminder on heraldic symbols) would be the aftermath of the Battle of Glen Fruin in 1603, as described thusly:

The MacGregors followed up the defeat of the Colquhouns by plundering and destroying the whole estate. They drove off 600 cattle, 800 sheep and goats, and 14 score horses, and burned every house and barnyard and destroyed the "Haill plenishing, guids, and gear of the four-score pound land of Luss," while the unfortunate chief, Sir Alexander Colquhoun, looked on helpless from within the walls of the old castle of Rossdhu, the ruin of which still stands on its rising ground behind the modern mansion.