Image courtesy of http://megaloman.proboards.com/index.cgi?action=display&board=beta&thread=990&page=1#6345
Toripuru Faita, or Triple Fighter, was a tokusatsu series that aired in 1972 for 26 episodes, each episode split into six-minute chapters.
Siblings Yuuji Hayase (Red Fighter), Yuri Hayase (Orange Fighter), and Tetsuro Hayase (Green Fighter) of the Space Attack Team fight against the Demon Star Empire's Devil Seijin and his Devil Monsters. When a monster-of-the-week proves to be too powerful for the three individually, they combine into Triple Fighter. Their allies are the mischievious Atsushi Oto and the mobile computer Bulcomm, which watches over their base.
The three's modes of transportation (an ordinary car and motorcycle) look suprisingly normal in comparison to what the villains use (small black Volkswagen Beetle-like cars with a cursive "D" on their hoods).
All of the monsters look similar to the cars, complete with the "D" on their belts, and wear unusual masks that are never taken off.
Here's the theme song: