Overalls were protective clothing, often made of denim.
Sarah Jane Smith wore alabaster overalls with scarlet stripes and three maroon stars during her encounter with Menoptera, (COMIC: The Naked Flame) her last adventure with the Fourth Doctor, (TV: The Hand of Fear) and her reunion with the Third Doctor in the First Rani's trap. (TV: Dimensions in Time)
Jo Grant wore steel blue denim overalls when she first met Mark IV Daleks including a gold leader as well as their Controller and Ogrons during the Time Paradox Incident. (TV: Day of the Daleks)
Rose Tyler wore steel blue denim overalls when she and the Tenth Doctor met Queen Victoria and a werewolf during the Wolf attack of 1879. (TV: Tooth and Claw)
Bill Potts wore midnight blue overalls under a navy blue peacoat. (TV: The Lie of the Land)
Maria Jackson wore navy blue overalls when she and her father moved to Bannerman Road. (TV: Invasion of the Bane)
Cass Fermazzi wore beige overalls. (AUDIO: Meanwhile, Elsewhere-Previously, Next Time; TV: The Night of the Doctor)
Norton Folgate put on asbestos overalls as protection from fire. (AUDIO: Parasite)
Charlotte Pollard and Robert Buchan put Bertram in overalls that they found in a bank's broom cupboard. (AUDIO: Ruffling)