Here is the first "screen test" of Boba Fett for George Lucas that took place on June 28, 1978. At this point, Boba Fett's armor was all white, based on concept art by Joe Johnston with Ralph McQuarrie. According to an article about "Proto-Fett" that previously was at StarWars.com, the white was "possibly a vestige of his 'Super Trooper' origins."
In (the) black and white video, sound designer Ben Burtt "hosts" Fett's reveal for Lucas and crew, describing the different weapons, functions, and characteristics of the costume (worn by Empire's assistant film editor Duwayne Dunham for the test). The somewhat amusing footage depicts Fett with a mocked-up laser rifle (which used a lightsaber hilt for the barrel) and a Star Wars beach towel doubling as the bounty hunter's tattered serape."Proto-Fett: The Birth of Boba" (Archive.org)