CGA Graphics: Not All Cyan and Magenta!

Saturday, 29th July 2023

Part 3 of a blog series on CGA palettes. Originally posted on my personal web site in 2020.

Reading the original BASIC manuals for my first PC, I found out what CGA claimed that it could do in 320x200 mode. Firstly, it allowed you to select one of the following two palettes for your three foreground colours: green, red, yellow, or cyan, magenta, white.  While this binary choice is limited, we already see possibilities.

A game set in a snowy landscape would benefit from the palette with white and cyan. White obviously is the natural colour for snow, and also allows clouds in the sky. Cyan is a good substitute for blue in the sky, and can also be used for shading on the snow. Magenta isn't particularly naturalistic in any setting, but serves as a contrasting colour. Coupled with the default black background, this palette also seems like the natural choice for space games.

Red, green and yellow suits a variety of other settings. The green helps with anything involving plants, and the red is a reasonable substitute for brown in things like tree trunks. Yellow or red function well as dirt on the ground, and the yellow would also be suitable for a desert setting. What's missing is a realistic colour for the sky, dramatic sunsets aside, so the palette would better suit a top-down or isometric perspective where the sky is not visible.

What the BASIC manual didn't tell me is that you can select dark and bright versions of these palettes. The first palette in its dark form becomes a darker turquoise, purple and light grey: it looks somewhat murky but has the same overall character as its brighter equivalent. The red, green and yellow palette undergoes a more subtle change, though. The dark red, green and brown provide an almost naturalistic set of colours for forest or jungle games.

Another common technique opened up a third pair of palettes. The 320x200 mode was actually a pair of modes, one colour and one monochrome. Selecting the monochrome 320x200 mode when attached to a colour monitor gave a surprising palette. Not the two greys and white that were all part of the 16 colour CGA palette, but cyan, red and white in either dark or bright versions.

Of all the colour sets offered by CGA in 320x200 mode, this is probably the most useful of all. It's only subtly different from the default palette, but the replacement of the gaudy magenta with a more naturalistic red allowed some settings to be more accurately rendered. The red and cyan was ideal for a rocky landscape and sky, with the white available for clouds, buildings and contrasting stones on the ground. A Martian landscape becomes a possibility.

In fact, while trying to think of settings that would suit the cyan, magenta, white palette, I came to the conclusion that any of the possible ideas that came up would look better in the cyan, red, white palette instead. If you can think of an idea in which magenta would look better then please suggest it to me! I'm on the lookout for ideas in which the magenta palette shines.

So far I haven't mentioned the other possibility mentioned in the BASIC manual: changing the background colour. This opens up a whole host of possibilities which I'll discuss in the next post.