It was a larger one with green sides. It came to the smaller, browner one and stayed there for about 20 seconds before the other one crawled away.
I am not sure if I had mentioned this before or not (because I am having trouble searching it in my older posts), but many weeks ago, one of the Taiwan Barbet's resting cavity had been taken over by ants. Well, my friend today helped me identified it to be Crematogaster rogenhoferi fabricans, a common ant in homes. Pretty cool, I think.