The following is from the book, Indian Wars, by Bill Yenne.
On September 15th, a thirty-six-man 10th Cavlary detachment was ambushed by a Cheyenne raiding party on Big Sandy Creek in eastern Colorado. Though they were outnumbered three to one, the Buffalo Soldiers successfully beat off the attack, with seven men wounded and none killed.
We have a slightly different version from the book, Encyclopedia of Indian Wars, by Gregory F. Michno.
Scouting along the road from the Arkansas River to Denver, Capt. George W. Graham of Company I, 10th Cavalry, a black unit, saw an Indian trail heading west. With his 36 troopers, Graham followed the path into present-day eastern Colorado. At Big Sandy Creek they ran into about 100 Cheyenne Dog Soldiers.
The warriors attacked and engaged the soldiers in a bitter fight at close quarters. It was Company I's first battle, and they handled themselves handsomely, fighting like "cornered wildcats."
By the time nightfall ended the fighting, 7 soldiers had been wounded and 18 horses had been killed or were missing; they had killed 11 Cheyennes and wounded 14.