[zero_iq]

This was especially common on 8-bit and 16-bit computers to fake 'high colour' displays on machines that had only limited colour capability. They often took advantage of the fact that people were using their machines with TVs with relatively slow-changing phoshor screens, so the flicker was less evident than on a modern monitor.

e.g. Photochrome on the Atari ST, was especially impressive at the time: https://www.youtube.com/watch?v=vPsY4P8bnVw

The most extreme version I've seen of this was on the ZX Spectrum, which had not only a very limited 15 colour palette, but also limited to 2 colours within each 8x8 block of the screen. Some bright spark came up with the idea of flipping rapidly between R, G, and B frames to give (limited) per-pixel RGB. Unfortunately it did flicker quite badly because of the extreme changes in colour levels (only two levels of each channel), and the fact that it required 3 whole frames to make a single colour virtual frame.

Example here: (not suitable if you have photosenstive epilepsy!) https://en.wikipedia.org/wiki/File:Parrot_rgb3.gif

[joosters]

Wow, that example parrot image is pretty impressive, given that it is just three colours, and I'm viewing it on an LCD!

I never knew anyone had tried that before on a spectrum. At first I thought you were just talking about the other trick, getting more than 2 colours per 8x8 by changing the palette as the raster scanned down the screen. The multi-colour parrot is way more adventurous!

I'd love to see the parrot image on an old CRT to get a feeling for what the effect might look like with the phosphor afterglow. Leaving the spectrum behind and using a bigger palette range, like on the ST, the effect seems much less epileptic fit inducing, because you can pick closer colours to switch between.