Yes, save for the stripe, the two are clearing almost the same. Now, This is true with several tartans. The Arbuthnott tartan, for example, is Black Watch, save for the addition of two white stripes in the sett (designed by Hon. Hugh Arbuthnott in 1962).

Do the Drummonds have their own tartan? Yes and no. The tartan normally associated with the clan is the same as Grant. The basic pattern appears to be from one called New Bruce. In 1819, Patrick Grant of Redcastle ordered 200 yards of this pattern, which was subsequently adopted by Clan Grant as one of their many tartans. Then, Clan Drummond adopted the pattern for themselves when they needed a tartan for the visit of King George IV in 1822. There is no such thing as a standardized pattern; therefore, historically there are variations of the tartan under both the Grant and Drummond names.

The tartan known as Drummond of Perth, referenced in this thread and the article you posted, is also the Perthshire tartan.

Now, don't let the tartan in the painting fool you. Many paintings of the Highland chiefs used tartans that were provided by the artist. For example, when Allan Ramsey painted the portrait of the 3rd Duke of Perth, he provided his own tartan. He seems to have used a Murray of Tullibardine tartan and changed colors for various chiefs. Therefore, the tartan in the portrait in the link you gave is probably not a Drummond tartan at all.


3rd Duke of Perth, wearing what is clearly not a Drummond tartan, but a variation on Murray of Tullibardine.