Graphics Ingenuity on ancient hardware In 2015, VileR and reenigne won Revision 2015's Oldskool Demo competition with their 8088MPH demo, which showed off wrangling 1024 colors out of CGA mode that officially only supported 16 colors... This well-written article is by VileR himself on tihs outstanding achievement discovered, as he puts it, "by equal parts chance and morbid curiousity." Here's his story... beautifully explained.
https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-illustrated/