Singing to open the plants was never really a problem, for reasons people have already mentioned above, it was just when I got to that boss fight that I got a little worried, because while I'm not totally color blind (red-green), it -does- mean that I generally can't easily tell close shades of colours apart.. which is pretty much all of the song colours ^^ There isn't a one on there that I couldn't mistake for another, so yeah, that fight was a little tricky.