Hi Bon,
I sometimes put an LED light inside, it really shows off the jewels, at night or in a darkened room. And you are right, on these particular lamps they are spectacular.
I can't tell if it is paint. Brass goes green through oxidation, and this lamp is probably 100+ years old.
If it is paint, it would be difficult to know if it is 'just green paint' or an early military batch bought off the shelf before they started stamping them USA.
Have fun, glad you are enjoying it.
Best Regards,
Adrian
(let's see if this message goes first time!)