Richard Bradley offers a set of Colonial Skirmish Rules.
De Bellis Indica is a DBA variant for warfare in India in the 18th and 19th Centuries.
Hordes of the Empire is a set of free wargames rules for playing 19 century colonial battles. It’s a variant of Hordes of the Things (HotT), which itself is a variant of DBA.
Joseph Morschauser’s wargames are designed to be played on a square grid. The Frontier Wargames set is for colonial games.
De Bellis Indica is a DBA variant for simulation of warfare in India in the 18th and 19th centuries. The basic scale is 1 figure = 50 men and 40mm = 100 paces