Avoiding analysis paralysis, making it more intuitive to manually write colors. But yeah, there doesn't seem to be any advantage over the well-established #ABC format than decimal digits being easier to non-techies.
replyNo, TFA does very deliberately and openly explain what the goal/justification is:
reply> Splash colours can help you avoid decision paralysis when picking colours. It's an emotional tool that stops you fussing around— trying to pick the "perfect" colour … It also means the user can deal with discrete / individual colour values in the drag-and-drop user interface. They don't have to deal with large numbers at all. Only one to nine
Ah so let’s avoid analysis paralysis by having only black, as Ford famously ruled for the Model T.
replyOf course that’s a reductio ad absurdum, but it’s also completely arbitrary to maintain that fewer options is better. The opposite is also equally arbitrary.