A beret was a type of hat.
UNIT soldiers and officers alike wore berets in the field. Over the years, the standard-issue UNIT field beret changed from khaki brown, (TV: Spearhead from Space [+]Loading...["Spearhead from Space (TV story)"]) to chocolate brown (TV: The Ambassadors of Death [+]Loading...["The Ambassadors of Death (TV story)"]) to green (TV: Terror of the Autons [+]Loading...["Terror of the Autons (TV story)"]) to United Nations blue (TV: Battlefield [+]Loading...["Battlefield (TV story)"]) to crimson. (TV: Aliens of London [+]Loading...["Aliens of London (TV story)"]) In a parallel world, UNIT berets were black. (TV: Turn Left [+]Loading...["Turn Left (TV story)"])
Sarah Jane Smith wore a red beret during her last adventure with the Fourth Doctor, (TV: The Hand of Fear [+]Loading...["The Hand of Fear (TV story)"]) and her reunion with the Third Doctor in the First Rani's trap. (TV: Dimensions in Time [+]Loading...["Dimensions in Time (TV story)"])
Sergeant Paterson wore a raven black beret during the Tremas Master's Survival Stratagem and his encounter with Cheetah People. (TV: Survival [+]Loading...["Survival (TV story)"])