The 500, launched in 1960, had won huge acclaim for its performance, but was criticised for having over-simple styling. So it was given a complete makeover. The result was the Colt 600. The exterior had long sweeping lines and the interior underwent overall refinements. The car retained the monocoque body and rear-mounted engine/rear-wheel drive configuration of the 500, but had a steering column gear shift, a bench seat and bigger fuel tank.

In the 1963 Malaysian Grand Prix, it took line honours as well as second and third places in the under 600cc class. Over 10,000 Colt 600s were produced up to May 1964 and it's recognized as being hugely influential in driving the company's growth.