Ok, since the "To Imbibe is to be led astray" clue took out the wine theories, I’m going back to another path I looked at earlier.
On Plate 56, if you move column to column from Old Lavender instead of by row, you hit
Flint (Grey). The book’s note for it mentions:
“The flints used for striking the spark in the old flint-lock muskets would also, by reason of the oil and grime, take on some such color.”
That pointed me toward the
Ferguson rifle, the breech-loading
flintlock designed by Colonel (later Major) Patrick Ferguson. The dirty Red Coat even had his own experimental unit called Ferguson’s Rifle Corps during the Revolutionary War. He died at the Battle of Kings Mountain on the border of the Carolina colonies.
"Mull over the Colonel’s past" made me look at the name instead:
Ferguson means “son of Fergus.” Fergus Mór was the legendary first King of the Scots and founder of
Dál Riata, the kingdom that included the
Mull of Kintyre.
"Mull over… says your kin." That geographic pun feels very much like the “William’s forest” style of wordplay earlier in the riddle. (Coincidentally, (maybe?) Paul McCartney has owned a farm on the Mull of Kintyre since the ’60s. Wings had a hit song by that same name that was the first single in the UK to sell over 2 million copies.)
I don’t have a solid tie-in to Part Two yet, and this could still be the wrong off-ramp, but it feels worth exploring now that the wine path is closed. Kagavi is having a nice laugh.
Maybe it'll provide someone else with some ideas!