Here's a diagram to help explain your point: https://etulipa.com/wp-content/uploads/2020/04/lightreflextion-CMY-RGB.png https://etulipa.com/wp-content/uploads/2

Here's a diagram to help explain your point: https://etulipa.com/wp-content/uploads/2020/04/lightreflextion-CMY-RGB.png https://etulipa.com/wp-content/uploads/2020/04/lightreflexti... The one on the right is Kaleido (CFA tech). See how you lose 2/3 of the light? Monochrome (and ACEP etc) doesn't have that problem. Just CFA. (This diagram is from Etulipa, and is meant to explain a benefit of their billboard-sized passive displays compared to CFA tech; Etulipa tech is really cool but it's not suitable for e-readers or desktop monitors, as they found out the hard way back in ~2010.) (CFA = Color Filter Array)