The flag of the U.S. state of Colorado was officially adopted on June 5, 1911. The flag, designed by Andrew Carlisle Carson, consists of a fess design of three horizontal stripes of equal width, with the top and bottom stripes colored blue, and the middle stripe colored white. A circular red "C", filled with a golden disk, sits atop the stripes. All aspects of the flag contain symbolism related to the state, as the blue is meant to represent the sky, the gold the abundant sunshine the state receives, the white the snowcapped Rocky Mountains, and the red the "ruddy" earth. The gold and white portions of the flag also represent the state's gold and silver mining industries, respectively.

The state had one previous official flag before the current one, from 1907 to 1911. The Denver chapter of the Daughters of the American Revolution, unaware that this flag existed, wanted to create a flag for the state and settled on a red and white colored one, designed with the help of then-state senator William H. Sharpley. This flag was presented to the legislature but, because it was less popular than Carson's design, it was replaced. The new design passed the Senate and House of Representatives on April 25 and May 6, 1911, respectively. The flag made its public debut at a parade on May 30, 1911, and was officially adopted on June 5, 1911. Further revisions were made by the legislature on February 28, 1929, to specify the exact colors used and on March 31, 1964, to specify the size and positioning of the letter "C" and gold disk.

In 1861, the Colorado Territory adopted the Stars and Stripes to be its official flag.

In 1907, Senators Lewis, Barela, and Anfenger introduced senate bill no. 155 to adopt an official state banner. The bill passed on April 9, 1907. Only two copies of the banner were known to have been created. One was held in the governor's office, and the other in the capital building auditorium.

In 1872, the Governor’s Guard militia was given a unique flag. The banner measured 4 x 6 feet, bearing the Territorial seal in the center and the name of the militia.

Colorado joined the union as the 38th state with the approval of President Ulysses S. Grant on August 1, 1876. An unofficial banner, consisting simply of the state seal on a blue background, was used beginning that year.

In 1882, two flags were given to the 1st Battalion of the Colorado National Guard from Denver. The regimental flag was described as: "6 x 6 1/2 in size, and is made of the finest double blue silk. On one side of the flag are the coat of arms of Colorado, hand painted in oil colors and the name and location of the battalion. On the reverse side is the coat of arms of the United States". The banner was made by Thomas M. Bowen. Four years later, Company C of the 1st Regiment Colorado National Guard was given a unit flag. The flag contain the state's seal in the center, with the words "Greely Guards, Co. C, Ist Reg't.,C. N. G."

In 1892, Governor Routt traveled to Chicago to discuss plans for next year's World's Fair. The Governor was sent a blue state flag with a state seal in the center. It was to be displayed at his auditorium. In 1898, the front of Colorado college was displayed a national flag and a state banner. In August of 1898, a group of young women from Colorado springs were tasked with making a state banner for Governor Adams. The banner was described as: "The groundwork will be of blue silk edged with heavy gold cord and fringe. In the center will be the gold and silver shield, having upon it the eye of divinity, and underneath the inscription. "Nil Sine Numine", the whole comprising the state coat of arms." It was painted by Louis Scatter with the materials coming from Mrs. Trimble.