The brown was more likely turning into the cocoon. They are beautiful moths. Some people suggest that you grow a few extra tomato plants just for the spinx moth to live on.
They are could be a Tobacco Hornworm or a Tomato Hornworm. I cant tell to well by the picture but they might be Tobacco Hornworms.
The tobacco hornworm (7 diagonal white stripes and, most commonly, a red horn)
and the tomato hornworm ("V" shaped markings with a horn that is often black). The
adult of the tobacco Hornworm is the Sphinx moth. The Five-spotted Hawk Moth is the adult of the tomato hornworm.
If the brown ones were eating the "old dried leaves" I would say that they were taking on the color of the food it was eating much like camouflage...