This is construct 3 plugin effects which can decrease the graphics output into 3,6,9 and 15 bit RGB. Low vomputer plugins using only webgl 2 and glsl es 3.Basically you will find all info about the Low computer output format on en.wikipedia.org/wiki/List_of_monochrome_and_RGB_color_formats
some demo
you can find it there : construct.net/en/game-assets/graphics/special-effects/low-computer-lofi-effects-3642
and you can visit and test the plugins online on my site : px-hybrid.com