Doc fixes

Doc fixes

* lisp/color.el (color-name-to-rgb, color-rgb-to-hex)
(color-hue-to-rgb, color-hsl-to-rgb, color-rgb-to-hsv)
(color-rgb-to-hsl, color-srgb-to-xyz, color-saturate-hsl)
(color-desaturate-hsl, color-desaturate-name, color-lighten-hsl)
(color-lighten-name, color-darken-hsl, color-darken-name): Doc fixes.