Colorado played virtually no role in the Civil War.
The Confederates did not occupy any part of Colorado and no southern troops were ever in the state.
The only action that took place in the state was between Union troops and Native Americans at Sand Creek.
This was not a battle but a massacre.
Many Native Americans were slaughtered by Union troops after they cooperated and set up camp near Fort Lyon in order to receive amnesty.
The following is a description of All Civil War battles in Colorado.
Other Names: Chivington Massacre
Location: Kiowa County
Campaign: Sand Creek Campaign (1864)
Date(s): November 29-30, 1864
Principal Commanders: Col. John Chivington [US]; Black Kettle, Cheyenne [I]
Forces Engaged: Third Colorado Regiment (approx. 700 men) [US]; 500 Cheyennes and a few Arapahos [I]
Estimated Casualties: Total unknown (US unknown; I 200)
Description: Scattered Indian raids had caused much ill-will between the white settlers and the Native Americans. In the autumn, Territorial (Colorado) officers had offered a vague amnesty if Indians reported to army forts. Black Kettle with many Cheyennes and a few Arapahos, believing themselves to be protected, established a winter camp about 40 miles from Fort Lyon. On November 29, Col. John Chivington, who advocated Indian extermination, arrived near the camp, having marched there from Fort Lyon. In spite of the American flag and a white flag flying over the camp, the troops attacked, killing and mutilating about 200 of the Indians, two-thirds of whom were women and children.
Result(s): Union victory (massacre)
Source: https://www.nps.gov/civilwar/search-battles.htm# No protection is claimed in original U.S. Government works