The following book outlines some history of these families:

Genealogical Memoirs of the Family of Colt and Coutts

History & genealogy of the Colts of that ilk and Gartsherrie, and of the English & American branches of that family (1887)

This book demonstrates the interchangeable use of the names Colt and Coutts. Interestingly it does say the Coutts familes of Aberdeenshire desended from the Colts of Fife. There was also a Auchertoul in Fife as well as Cromar