Answers to most of the Mototrbo questions can be found in the Mototrbo System Planner.
Here is some information on color codes and groups copied from that document: Color codes are defined by the Digital Mobile Radio (DMR) standard and can be used to separate two or more MOTOTRBO digital radio systems which operate on common frequencies. The total number of available color codes per frequency is 16. From a radio user's perspective the color code is similar in nature to a Group ID. However, it should not be used for this purpose. Just as Groups are intended to separate users into groups, the color code is intended to uniquely identify systems or channels which operate on common frequencies. In MOTOTRBO systems, capabilities for Group Calls are configured with the portable and mobile radio CPS. The repeater does not require any specific configuration for groups. Radios can be configured to enable the user to select among multiple groups using the radio channel selector knob or buttons, or using the radio menu contacts list. Which group a radio user hears on a given channel depends on a configurable parameter called the RX Group List.
