Common standard for defining a color?

Hi colleagues :-) Investing a bit further deep into the field of colors (for usage in new Image_Graph) I stumbled over a question that I'd like to have discussed on this list. How do we define a color? Let's start with RGB-color, since this will be the most used one: Image_Color uses an array with indizes 0,1,2: array($red, $green, $blue) Image_Text uses an array with indizes r,g,b to indentify the colors: array("r" => $red, "g" => $green, "b" => blue) I see a good point for choosing the Image_Color-way because the array is easier to construct. However I like the Image_Text-approach a bit more in reference to "easily readable code" etc. In which direction should we go? IMHO it would be good to decide on a solution that's used all across those Image_*-packages etc. because otherwise you would have to convert between those array-formats - not much usefull in my eyes. I'm thinking about a way to handle CMYK etc. also. So going the Image_Text-way might be preferable? Please comment expressing your feelings about this! And one more question that arises: How would I best add an alpha- value to those arrays? For the Image_Color-approach I would simply add a fourth value, for the Image_Text-way an "a" => $alpha. Right? imagecolorallocatealpha() defines a range of 0..127, whereas 0 means "completely opaque" and 127 "completely transparent". But since the colors have a range from 0 to 255 and 255 defines full intensity for a normal color, wouldn't it make more sense to use an alpha of 255 as "opaque"? Afaik an alpha-value of 0 is "fully transparent" in most programs, right? Pierre, could you please tell me a bit about this? Regards Stefan