One of my senseis says that, since O Sensei's staff techniques were base more on yarijutsu (spear fighting) than on any staff art, using color to designate one end of the jo as the "spearhead" might aid our understanding of some jo kata. I have never seen him (or anyone else, for that matter) attempt this, but I am inclined to believe him.
Can you name a jo kata where one end of the jo is the "spearhead"? That is, where the same
end is used to thrust or strike with throughout the kata?
(It's also worth noting that even if this story is true, jojutsu existed long before aikido, and jojutsu does not distinguish between the ends of the weapon. If we're doing yarijutsu in disguise, then let's use an actual yari...if that's what we're doing, which I doubt)