Hello Etienne, thanks for the patch.

On Wed, Apr 27, 2016 at 12:48 AM, Etienne Prud'homme 
<e.e.f.prudhomme@gmail.com> wrote:
> The attached patch adds completion for CSS color functions such as
> `rgb()'. Values were taken from the “CSS Color Module Level 4”. 
> It can
> be found at: https://drafts.csswg.org/css-color/#color-type

It will be nice to have completion for those new color functions. Some
feedback regarding the patch follows.

- In the completion definitions we've tried to stay as close as possible
  to the structure used in the CSS spec. This means that instead of
  introducing `color-functions' we should make `color' complete directly
  to "rgb()", "rgba()", and so on, then `hex-color', `named-color' and
  the literal `currentcolor' (I think we can skip
  `deprecated-system-color'). `named-color' will then contain the
  literal color names like `color' does now.

- One of the tests in test/lisp/textmodes/css-mode-tests.el needs
  updating. To see this, run `make lisp/textmodes/css-mode-tests' from
  the test directory.

- Please wrap lines around column 70 or so to stay in line with the rest
  of the file.

> As a sidenote, how should we handle functions? Since they use
> parentheses, the point is going to be outside of parentheses.
> 
> Eg.
> rgba()*
>       ^(point)

True, I'm not sure how to best solve it.

> Also, should we include the parameters number?

I think that's rather a job for something like ElDoc (I'm currently
working on adding ElDoc support to CSS mode).

-- Simen