back to your original question:
my owner's manual page 8-13 says,
DO NOT OVERFILL.
Use ONLY Nissan Matic D or Canada NISSAN Automatic Transmission Fluid.
but,
Dexron III / Mercon or equivalent may also be used.
additional note:
Outside continental USA and Alaska, contact a dealership for more information regarding suitable fluids, including recommended brands of Dexron III/ Mercon.
you in da USA?
back to that greenish fluid leak... is that coming from the AC system or your coolant system?
you can test the cooling system with a pressurized tester kit ( Autozone still has the tool-loan program for you to do this ~ a free service) that will eliminate any concerns with your cooling system