Macaulay was a son of the Rev. John Macaulay (1720–1789), minister in the Church of Scotland, grandson of Dòmhnall Cam. and his mother was Margaret Campbell. He had two brothers: Rev. Aulay Macaulay, scholar and antiquary, and Zachary Macaulay, colonial governor.
Macaulay served for thirty years in India, in the Company's army. He was present at Seringapatam, and was one of Sir David Bird's companions in the two years imprisonment under Tipu Sultan. He was for many years on intimate terms with the Duke of Wellington. He served a resident of the British East India Company for Travancore and Cochin during 1800-1810 and was the subject of an attack by Chempil Arayan. In 1811 he returned from India and took a little part in public affairs. He sat in Parliament for one Session (from 1826 to 1830) as Member for Saltash but did not take part in any debate. He was an active supporter of the British Bible Society and was engaged in the Abolition of Slavery. He became a member of the Society for the Abolition of the Slave Trade. He accompanied the Duke of Wellington to the Congress of Verona in 1822, where proposals were submitted for the entire Abolition of the Slave Trade.
- Hansard 1803–2005: contributions in Parliament by Colin Macaulay
|Parliament of the United Kingdom|
| Member of Parliament for Saltash
1826 – 1830
With: Andrew Spottiswoode
Earl of Darlington