[chrismorgan]

Things like colours and units get used in many properties (color, background-color, border-color, box-shadow—in which <color> is only a part of the syntax—and many more; width, length, font-size, font—a shorthand in which <length> is only a part—and many more), and if they get expanded in one place, then all properties that use them take the new definition—hence <color>, <length>, &c. as the only sensible way to structure things (in spec, reference and mental model). By contrast, the values of properties like ‘display’ aren’t used anywhere else.

It sounds like a large part of the problem is helping to build the right mental model. If you understand that colours and lengths are used in many places, it will make sense that they will be documented separately from the properties, and that the properties’ references will just refer to them.

[itsuka]

Thank you for taking the time to explain things so clearly to me. Considering the reuse, having values in a separate page makes sense now.