Sunday, 8th February 2015
As part of my retro-computing hobby, I've been playing with colour palettes on an ancient computer. In this case, it's an old-fashioned PC with 4-colour CGA graphics. You might remember the early days of PCs, where all the games seemed to use the same shades of black, magenta, cyan and white.
CGA actually had 16 colours. When using graphics, you could use four of them at once. But your choice of which four was more restricted than on computers like the BBC micro or Amstrad CPC. These two computers had similar medium-resolution 4-colour graphics modes, but allowed you to choose any four colours from the machine's palette.
CGA allowed you to choose any background colour, but restricted you to one of a set of six palettes for the other three: cyan, magenta, white; red, green, yellow; cyan, red, white; and darker versions of those three palettes. You'll occasionally see black/red/green/yellow (or black, dark red, green and brown) in some games, and a few used the red/cyan/white combination.
But very few games bothered to change the background colour. And this is a shame, because using the background colour would give a choice of 78 four-colour palettes. Not all of them are useful, but there's a lot more variety in the CGA palette than so many old games would have you believe.
Since it's difficult to visualise all the palettes and how they'd look, I've prepared a graphic for my own use. If anyone else fancies developing a game supporting the old 4-colour CGA graphics card, then you might find it useful too.