By 1817 Colin Mackenzie of Mountgerald (c1767–1824) was joint owner, with William Fraser of Culbokie, of plantation Union, on the west sea coast if Berbice. Their attorney was Lewis Cameron [Slave registers].
In, or soon after 1795, Mackenzie had married Emilia, a sister of the Belladrum Fraser brothers. Late in that year Harry Robertson wrote from Demerara to his sister in Kiltearn saying 'I am told Colin McKenzie of Mount-Gerrald was bold enough to encounter Miss Fraser of Belladrum and has succeeded; he is I hear become a soldier again; who are his officers? — he would be better follow his calves & let that trade alone.' [NLS MS 19332 f24]
There is no evidence that Mackenzie went to Berbice. His son, also Colin [1802-1837], became a clerk in the London merchant house of Davidson of Tulloch and then went to Jamaica, where he died aged 35 [Pigeon holes of memory: the life and times of Dr John Mackenzie (1803-1886), ed Christina Byam-Shaw (1988)].
He was commemorated in the cathedral at Spanish Town:
Sacred to the memory of COLIN MACKENZIE, Esquire, of Mount Gerald, Ross Shire, North Britain, and of Spanish Town in this Island, who departed this life on the 1st December 1837 aged 35 years. The honourable conduct the kind disposition and the amiable manners which distinguished this gentleman through life endeared him to many friends in this Island who have erected this monument to his memory as a testimony of their regard and esteem.
Fraser and Mackenzie claimed compensation of over £9000 for the emancipation of their 176 slaves but £7000 was owed in morgages to J. T. & A. Douglas. [Legacies of British Slave Ownership]