Jax makes a green and I think a copper plate of some sort. Jax
Chemicals.
There are other colors, all results depend on how much work you put into the
application. None are "simple".
As mentioned, Jax chemical is the most widely used. In order to get green,
you need the copper plate(not patina) to get those results, along with a
darker brown. Most patinas applied cold are rather fragile, especially when
first applied, and certainly while still wet.
Try those first Bob, then get into some chemistry, there is arather
expensive book out there called the Bronzing and patination of metals, which
mostly covers copper based alloys. ( copper, brass and bronze) plated
srufaces included.