The RCAHMS website says that "An inclined standing stone was recorded at this location through fieldwalking in areas of the eastern side of the island of Coll." - this was in 2003.
I wonder if it was the stone mentioned here in the 'Life of Johnson' by James Boswell ( it is on the way to Breacacha castle):
We set out after dinner for Breacacha, the family seat of the Laird of Col, accompanied by the young laird [..] We passed by a place where there is a very large stone, I may call it a rock; 'a vast weight for Ajax'. The tradition is, that a giant threw such another stone at his mistress, up to the top of a hill, at a small distance; and that she in return, threw this mass down to him. It was all in sport.
Sheer speculation I admit. It could probably be any number of stones on Col. Found in vol V - 'journal of a tour to the Hebrides with Samuel Johnson' 1773. Online at Google Books. Supposing you know the true stone this relates to - please leave a comment.
Later on they went to see the other 'great stone' in the story. I'm afraid to report that it "did not repay [their] trouble in getting to it."