this is a tricky one. what is displayed here is a 4-color-picture colored by code in a sense.

it is part of the demo coma light 13 and was intended to get moved by a line scroller to get a perspective feel to it. the mode is multicolor bitmap and because the coder needed control for the color ram i decided to create monochromatic versions of all settings. those looked like this one:
vetodrom.com/media/oxy/scroll/height2.png

those are still 5 colors and did not match the overall shifting, so the pics needed to be post processed. the result looked like this:
vetodrom.com/media/oxy/scroll/output.png

there are a few more details to keep in mind, like that the coloring could only change 2 colors per setting in the fix area (mid grey needed to stay the whole sequence) and in the scroll part it was like changing single colors like roller shutters - looked like tearing when too many colors changed the same frame. to get this effect reduced the brightest color stays most of the time and the second brightest is specified as background (because it is not affected by this effect).
last but not least a rasterbar fade has been added in the upper background. steam and birds are multicolor sprites.