How to do a Status Indicator (RYG) roll up by Department?


I've created a project plan where every task has an automated formula to indicate the status (red, yellow or green ball). Each task also has a department associated with it.

For example: Marketing department has 15 tasks that has various red/yellow/green status balls associated with each task.

Is there any way where I can "roll up" all the RYG balls to provide only 1 status indicator for the entire department's task? (Hope I am making sense)