So with no indizes at all, in your eyes? Just plain int-arrays, consisting of 3 values (rgb) or 4 values (rgba)? How would we represent cymk or other formats?
What I see now is that there are so many color standards out that it's needed to have a color format prefix always. However, we use RGB or RGBA more often than the other formats (because it's the standard for the web) so in my opinion RGB/RGBA may be the default values if not otherwise specified.