There is no shortage of free wargames rules for the Colonial period. A good one is the Two Page Skirmish rules from Steve Winter.
skirmish
Lord Merlin’s Rules of Engagement
Lord Merlin’s Rules of Engagement is a set of free wargames rules for medieval style wargames. What makes these unique is that they are designed for large scale (70mm) figures. Despite the “Lord Merlin” monicker, there doesn’t seem to be a fantasy component here.
Black Powder Skirmish Rules
Black Powder is a set of free wargames rules by Wes Rogers for skirmish warfare in the period 1600 – 1870.
Danegeld and Dragonships Dark Age Skirmish Rules
Danegeld and Dragonships is a set of free wargames rules for dark ages skirmishes. It has an interesting turn mechanism in that the side that gets the most kills has the initiative the next turn.
Simple Samurai Skirmish Rules
The older I get, the more I like simple rules sets. Here’s one for Samurai Skirmishes.
From the introduction:
Sensō is a skirmish game, 1:1 figure scale, for 25mm miniatures. One scale inch represents six feet and one turn roughly approximates one-two minutes. Bases should be square for foot, approximately one inch. Mounted can be 1” x 2”. The game is WYSIWYG (What you see is what you get); figures are armed and armoured as they appear.