Color keywords are replaced when prefixed with --

[seamusleahy]

When a color keyword is prefixed with --, the value is replaced with the hex value. Other uses of the keyword are not replaces with the hex value.

Input: body{background: magenta; color: var(--magenta); border-color: var(--color-magenta);}

Output: body{background:magenta;color:var(--#ff00ff);border-color:var(--color-magenta)}

[nschonni]

Although the title may be different this is a dupe of #1624. You can track the issue/upstream issue there.

[xzyfer]

This issue elaborates on the issue with colour names further: sass/sass#2128 (comment)

You should never use a colour name unquoted in Sass. However Sass 3.5 will have better support for custom properties (--red) http://blog.sass-lang.com/posts/809572-sass-35-release-candidate. This feature has not landed yet in node-sass.