Not sure myself, I like how they differ a lot, well when I like them anyway
Like the custard cream one, the orange one, this seasons maroon one, liked the white puma one (not as much as the white Adidas one with sky blue on it, or the white Brown ale one )
If it was the same colour all the time we'd end up with horrendous spikes or post-it-note like patterns when they run out of ideas