Big Jim is right on the key colors. The majority of Libertys have it! Any kind of remote keyless entry module usually has SKIM, too.

You should check with your local Chrysler/Jeep Dodge dealer, have them run your VIN to see if the Liberty originally came with the SKIM (Sentry Key Imobilizer Module) system. If so, it's possible that your key is bad, and/or the SKIM module is bad or not communicating over the vehicles bus. A new key and/or SKIM module would need to be programmed using a secret code and a scan tool capable of communicating with the SKIM module and the PCM. The dealer can supply you with the secret SKIM code, but you probably will need to bring proof of ownership to get it from them. A new key is usually around $60, with maybe .5 to 1 hour labor to program it.