Color has always played a key part in the style of video games, and the evolution from 2 to millions of on-screen colors parallels the advancement in game console technology. This bright, cheery infographic shows how far video game colors have come from the days of Pong and Pac-Man.
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NEC's Handheld the TurboExpress could also handle 512 colors and used the same cartridges (HuCards) as the TurboGrafx-16. The battery life was I guess about 3 hours. But I never had a problem with the battery, I was just happy to have a color system that played the exact same cartridges.
I also had a game gear, and my friends had Gameboys. Over-all, I never noticed much difference in battery life, but we'd just plug them in when needed. My favourite was always TurboExpress, then Game Gear, then Gameboy.