Yes I've come across from time to time books saying that the early philabegs issued in the Black Watch had a red line, and/or that the philamores of the Grenadier Company had a red line.

I don't know what the actual primary source (if any) is for this... however Donald C Stewart in The Setts of the Scottish Tartans has this to say

"We are told by Logan (author of The Scottish Gael 1831) that the 42nd, in his time, were some of them to be seen with a red line in their tartan, the explanation being that this was added by a Murray of Atholl, who commanded the regiment, and made the tartan resemble the Athol. In the Murry tartan that he (Logan) gives the red line is centred in the green, though in the Athol Murray as we know it there is a red line in every green band and also in every other blue."

To the casual observer these tartans look quite different, the Black Watch with the added red line having only single lines while the Athol Murray tartan has a pattern of three red lines.