Would it be possible to add a check to see if the altar is within the PC's range of vision whenyou 'l'ook at it? If so, then one possible solution would be to have the altar's colour reported in those circumstances, but not if you're further away. Alternatively, have it report the altar's colour if you're standing right next to it, in the same way you can identify items by 'l'ooking only when you're adjacent to them.
I definitely think that this issue should be addressed somehow, though. It can be very annoying not to be able to tell an altar's allignment without taking the potentially fatal step of standing on it.