because the chinese symbol ('word') on the album's cover means 'purple' in english..and it's no coincidence, STP wanted it to be called Purple obviously, cause they thought it sounded purple...
you know, like some music makes you think about dark colors, and some peaceful church songs might make you think white or something, and STP boys thought purple off of the songs they'd written, and named it like that, but for some reason wanted it to be written in chinese, and asked some cook in a chinese restaurant how the symbol (word) would look in chinese..