Remove rgba() and hsla(), redirect to rgb() and hsl() ?

[wbamberg]

We have separate pages for rgba() and hsla(), alongside the pages for rgb() and hsl(). But the spec does not document the ...a() form as its own thing. For example, see https://w3c.github.io/csswg-drafts/css-color/#rgb-functions - it only describes rgb(), and then says:

an rgba() legacy color syntax also exists, with an identical grammar and behavior to rgb().

...so the rgba() form is described as a legacy syntax for rgb().

This causes some problems for our standalone rgba() and hsla() pages. For example, formal syntax is not available for for hsla() and rgba(), so either we omit it (unhelpful) or use hsl() and rgb() (confusing).

I think we should follow the spec here and:

• remove these legacy pages
• redirect them to the current version
• include a note there about legacy syntax.

Related: mdn/content#23238, mdn/content#23236.

[wbamberg]

We discussed this in the Steering Committee meeting and people are happy to go ahead as long as there's a clear note in the target pages about the legacy forms, since many people use/have used them.