It is also misused in color printers which leave a repeating pattern of small yellow dots encoding model, serial number, and so on, so your newly printed money

It is also misused in color printers which leave a repeating pattern of small yellow dots encoding model, serial number, and so on, so your newly printed money will provide a nice paper trail back to you. Also, yes, handling of colors and color combinations is a very old topic, just that this knowledge isn't given to us by birth, but through learning. Which means there will always be someone stumbling over this and make another post delving into (some of) the details. As long as it brings others up to speed, I count this as a net win. One can just hope that the history isn't lost entirely eventually ...