The Fox Suspension fluid in your Fox fork should be changed every 30 hours. If you do this, you don't have to replace your seals every time. Most people don't heed this warning, but if you're riding a lot, you should at least have your fork overhauled every year (at the very least).
32oz will last you a while.
The Green fluid is for the Oil Bath on FIT forks. The Red Fluid is for the Fit Damper (it will also work for old Open Bath forks, but requires a little more work.
|Option||Manufacturer's Part Number||Store SKU|
|Green 10wt (Oil Bath) 32oz||025-03-008||FOX38822577N|
|Red 10wt (Damper) 32oz||025-02-003||FOX2172903Z|