I found the MacKay book on Electric Scotland, here. Here's what MacKay said about the tartan that he calls Clanranald full dress.

"For the pattern, which we have no hesitation in giving as the Clan Ranald full-dress, we are indebted to Mr. Allan R. MacDonald of Water- nish, Skye. It is taken from a plaid spun and dyed by an ancestress of Mr. MacDonald's, a daughter of Lachlan MacKinnon of Corry, the entertainer of Dr. Johnson and Pennant, and worn by her husband, Allan MacDonald of Baile-Fhionnlaigh, Benbecula, a cadet of the Clan Ranald family, as a captain in the Clan regiment of the 45, and who was severely wounded at Culloden, whose portrait, dressed in the tartan, is shown on page 166. The plaid is a beautiful specimen of the old Highland hard tartan, and m.ade of the wool of the aboriginal Highland sheep—the colours are still quite fresh and bright. According to John MacCodrum, the bard, c. 1715, the colours of the Clan Ranald tartan were crimson with carnation in the waft."
He also has a plate of Sleat with a different backstory and one of a very similar tartan to this called Glengarry. He calls the similar tartans we know as Clan Donald, Clanranald and Glengarry hunting variants.
Here is the portrait he references. I'm not sure how the tartan is question is demonstrated here.

Edit: How reliable a source is MacKay?
Last edited by Nathan; 13th April 14 at 07:07 AM.
Natan Easbaig Mac Dhòmhnaill, FSA Scot
Past High Commissioner, Clan Donald Canada
“Yet still the blood is strong, the heart is Highland, And we, in dreams, behold the Hebrides.” - The Canadian Boat Song.
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