Red, Yellow, Green.
This plugin allows you to create a new Traffic Light custom field that you can associate with any existing system or custom field. You can then add rules that determine which colour to paint this Colour field, based on the value of the associated JIRA field. For example all issues in with priority critical and a specific assignee may be colored orange. Use the full power of JQL to define your rules. To install this plugin in JIRA 4.3 please first install Active Objects as defined here.