What is a color space? — Making Software

Colour spaces give software a shared coordinate system for describing colours that different devices can reproduce consistently. The apparent simplicity comes from a set of carefully chosen representations, transformations and physical assumptions working together.

Models and spaces

RGB is a model; sRGB and Display P3 are spaces with defined primaries, a white point and transfer curve.

This is one part of a longer chain: wavelengths becomes cone response becomes coordinates becomes display gamut. The useful abstraction hides the physical work, but the underlying constraints still shape the software built above it.

A bounded gamut

Every colour space encloses a limited region of the colours humans can perceive.

The implementation is full of compromises. Precision, speed, storage and energy rarely improve together, so practical systems choose the errors people are least likely to notice.

Translation

Colour management uses profiles to map values between cameras, files, displays and printers.

Once this layer is visible, familiar design conventions stop looking arbitrary. They are accumulated responses to the capabilities and limits of the machinery below.