0004 — Colour is Ink: RGB, CMYK and spot, with tints

Status: Accepted

Context

Colour was RGB only, with the Material Design palette built in. Print production needs more: CMYK process colour, and named spot inks (PDF Separation colour spaces) for brand colours and special inks. A managed writer makes these cheap to support, and few .NET PDF libraries offer them.

Decision

Colour is modelled as Ink, in three kinds: RGB, CMYK and spot (a named ink with a process-colour fallback). Tints behave as in print — a percentage of the ink. Only a handful of named inks ship (black, white, registration, transparent); the Material palette is removed, and users bring their own colours.

Consequences

• Print-ready output without post-processing, which is a genuine differentiator.
• Blending, gradients and transparency must be specified per colour space.
• Code using the Material palette must migrate; there are no external users yet.