Are you sure it's not Yellow? Amber is 4x Amber LEDs, no green in them. SF Yellow is 3 Amber, 1 G. If you had Amber the whole time and are randomly getting Green coming on, there's likely something wrong with the LED, possibly with the Green diode itself.
Another question: What saber model is it? If it's one of the Apprentice hilts, it's very likely that you crushed the resistors against this inner ring/flange they have when shoving the LED back down the neck of the saber. I did that to the LED in my Arbiter and had to have it repaired as one of the wires was nearly sliced in half.
Last question: When you say it "won't turn on", do you mean the blade, or the blade AND sound? If you're getting sound but no light, then it's an LED or LED wiring issue. If you're not getting either, then it's another issue; likely a faulty recharge port.
Solutions: Contact SF (This email address is being protected from spambots. You need JavaScript enabled to view it.
) about Warranty repair, if the saber is under 1yr old (which I'm guessing it is). You'd need to fill out an RMA form and send that with it if they approve the repair. If they don't approve it, or it's too costly for you to ship it back (such as if you're overseas), then there's a few people on the forums here who could repair it for you.