Why are there always color differences in prints?
The difference or distance between two colors is an important metric in color science. It allows quantitative examination of concepts previously described only with adjectives. Quantification of these properties is important for those whose work is critical to color. Generic Definition Euclidean distance is used in a device-independent color space.
Since most definitions of chromatic aberration are distances within a color space, the standard way to determine distances is Euclidean distance. If you currently have an RGB (red, green, blue) tuple and want to find the color difference, one of the computationally easiest ways to do this is to consider the R, G, B linear dimensions that define the color space.
This is useful when comparing a single color to a single color and need to simply know if the distance is greater. If you add these squared color distances, such a measure actually becomes the variance of the color distances.
There have been many attempts to weight RGB values to better suit human perception, where the components are usually weighted (30% for red, 59% for green, and 11% for blue), but these are significantly worse in color determination, and correctly Contributes to the brightness of these colors rather than the degree to which human vision is less tolerant of these colors
