~.~.
My parents have a dual flusher. The buttons are a smaller circle inside of a bigger circle. You push the bigger one for number one and include the smaller one for number two. I can't tell that much of a difference, other than the water runs a little longer if you push both.
ETA: The small button on my parent's toilet is green and the big button is silver. Yellow and brown buttons would make it obvious, but it would be pretty ugly.