Re: [csswg-drafts] [css-colors-4] Clarify whether RGB is additive or not (#9977)

However, to give you something to go on meanwhile, additivity is one consequence of [Grassman's Laws](https://spie.org/publications/pm105_31_grassmann_laws) which form the basis of modern colorimetry (subject to certain conditions, which that link also states). And they are generally true but can break down under certain conditions, termed _additivity failure_. As an example, if human subject color matching tests are performed to match a given hue at different levels of chroma, the results do not exactly fall on a straight line on a chromaticity diagram but on a _slightly_ curved line.

 - [Color sameness: what to do when Grassmann additivity fails experimentally](https://www.spiedigitallibrary.org/conference-proceedings-of-spie/1909/0000/Color-sameness--what-to-do-when-Grassmann-additivity-fails/10.1117/12.149083.short)
 - [Perceived brightness of of whites with lower and higher chroma display primaries (additivity breakdown from the Helmholtz–Kohlrausch effect)](https://sid.onlinelibrary.wiley.com/doi/full/10.1002/msid.1392)

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Received on Tuesday, 20 February 2024 21:01:05 UTC