The Model 1898 Khaki uniform was first developed in June, 1898. This uniform was made in response of the needs of American soldiers fighting in tropical climates, such as Cuba, Puerto Rico and the Philippines. With this uniform, the collar, false cuffs and epaulets were made in the branch facing color of each soldier. The uniform seen below is from a Volunteer soldier. The official regulation did not have the pocket flap faced with the branch color. This was done as a submission to fashion and normally only done by Volunteer troops. The buttons on the uniform also corresponded to the individual soldier's assigned branch, especially for officers.
U.S. Army Quartermaster Department, Regulations and Decisions pertaining to the Uniform of the Army of the United States, Second Edition, 20 June 1898, (Washington, Government Printing Office, 1898).