They were responsible for conducting the business of the Governor with the various Government Departments and also with the colonists, collectively and individually.
The Colonial Secretary was a member of both the Executive and Legislative Councils.
Often, Colonial Secretaries became responsible for a variety of functions, including customs, post offices, shipping, harbours, prisons, and natives.
The Colonial Secretary often also dealt directly with England.
[1] The role was often quite flexible depending on the Governor, as the Colonial Office was reluctant to define the role precisely, fearing it would become redundant.