Color Models
Color Models
[A simple flowchart is shown. The text above the panel reads:] Evolution of my understanding of color over time:
[On the left side is a vertical dashed line in gray, on top it's labeled:] Grade school [And at the bottom the label reads:] Now
[Header above the chart:] "Color" is...
[The chart starts with three items, one left and an other on the right, a third is below in the middle.] ...three primary colors mixed together ...a rainbow, and each color is a wavelength ...unknowable ("maybe what I see as blue, you see as...")
[Arrows from the left and the middle item point to a new left one, while two other arrows from the middle and the right item lead to one at the right.] ...three-ish primary colors mixed together (RGB/RYB/CMYK) ...a mix of infinite wavelengths filtered through three eye pigments
[The arrows of both items point to one in the middle:] (something about the opponent color model)
[The remaining items are all in the middle and each is connected by one arrow downwards to the next.] ...an abstract multidimensional gamut (CIE 1931, L*a*b*, etc) ...an abstract multidimensional gamut filtered through inconsistently-implemented device color profiles ...a hyperdimensional four-sided quantum Klein manifold? Is that a thing? ...hopefully somebody else's problem.

Randall is describing how his level of understanding of colors has changed by age. The chart starts with two tracks of understanding color.
In grade school he learned about the primary colors, and the very simple model of colors, as shown in the left track. Mixing of color solids, as in painting (or finger painting being probably the earliest exposure to color mixing), is intuitive for a child. The process is subtractive, and the more colors you mix the darker and closer to black you get. Color is seen by the eyes when light bounces off the solid colors and becomes light of different wavelengths that the eye can then see. However at this level, things just "look" like different colors without understanding light's role. The color models mentioned in the second point of the left track are the additive model RGB (red-green-blue) and the subtractive models RYB (red-yellow-blue) and CMYK (cyan-magenta-yellow-key, used in color printing).
The right track is about mixing of colored light, as in prisms and light waves, where mixing colors is additive and the more you mix the lighter and closer to white you get. But this is without a real understanding of light bouncing off surfaces, and is limited to an understanding of different colors of light and how they mix. The first exposure in grade school is usually by shining white light through a prism to separate it into the different visible colors.
Meanwhile, philosophically, color is unknowable because it's impossible to say if everyone has the same qualia for colors. E.g. "Maybe what I see as blue, you see as my idea of purple, but we both call it blue because we've been brought up to know to call that color blue?."
The opponent color model connects these two models, by considering how the signals from rods and cones are processed, after different wavelengths of light are absorbed by different rods and cones in the eyes.
The "complex multidimensional gamut" mentions two more models: CIE 1931 and L*a*b* . These are more detailed models based on the opponent color model, which precisely define how a particular color maps to the different channels that our eyes see.
However, understanding how the eye sees color still isn't enough, because not every device can display all the colors your eye can see. Your laptop might have a different gamut from that of your phone, and when you print the page, you might see yet another color. To handle this issue, web browsers use "color profiles", so that an image can be tagged with the color space it uses and the browser can handle it appropriately. Unfortunately, browsers do this inconsistently and not very well.
Further complicating the matter, ostensibly identical device may show colors differently (depending on how they are adjusted, variations between devices, aging of the device, and the viewing environment).  Devices and software exist to attempt to match systems to reproduce colors consistently, however  most systems are not set up this way, color correction can be complicated, and the corrections have to be frequently readjusted.
The "hyperdimensional four-sided quantum Klein manifold" is a joke, and could also be a pun upon the color Klein Blue . A Klein manifold is described by the Klein bottle , where the bottle was originally a surface (a mix-up of the German words Fläche for surface and Flasche for bottle). It is a two-dimensional manifold, or simply just a surface with some special characteristics. Randall is here projecting an "abstract multidimensional gamut" onto an even more complicated surface, presumably in order to eliminate the errors in color rendering caused by previous attempts to eliminate the errors in color rendering. The Klein bottle has to be projected into 4 dimensional (4-D) space for this to work, as it would otherwise intersect with itself.
The “quantum” may be a reference to the "color" charge in Quantum chromodynamics .
Eventually it appears Randall has given up, realizing color is very difficult and hoping somebody else will deal with the difficulty in describing, understanding and using the concept of colors.
The title text expands on this joke, implying that the reason for the "unknowable" answer in the comic is that everyone's browser shows colors slightly differently. Despite the complexity and thoroughness of color models, this common software can't get it right.
[A simple flowchart is shown. The text above the panel reads:] Evolution of my understanding of color over time:
[On the left side is a vertical dashed line in gray, on top it's labeled:] Grade school [And at the bottom the label reads:] Now
[Header above the chart:] "Color" is...
[The chart starts with three items, one left and an other on the right, a third is below in the middle.] ...three primary colors mixed together ...a rainbow, and each color is a wavelength ...unknowable ("maybe what I see as blue, you see as...")
[Arrows from the left and the middle item point to a new left one, while two other arrows from the middle and the right item lead to one at the right.] ...three-ish primary colors mixed together (RGB/RYB/CMYK) ...a mix of infinite wavelengths filtered through three eye pigments
[The arrows of both items point to one in the middle:] (something about the opponent color model)
[The remaining items are all in the middle and each is connected by one arrow downwards to the next.] ...an abstract multidimensional gamut (CIE 1931, L*a*b*, etc) ...an abstract multidimensional gamut filtered through inconsistently-implemented device color profiles ...a hyperdimensional four-sided quantum Klein manifold? Is that a thing? ...hopefully somebody else's problem.
