Current status and Status trend fields are subjective and manual entries.  

The Current Status of an item can be on schedule, at risk, etc.  The Status trend is from a historical perspective in relation to how this item has performed in the past and can be on schedule, at risk, etc. 

The color coding is based on the picklist value that is chosen, e.g. On Schedule = green; At-Risk = orange; delayed = red; Complete = blue, and Not Set = Gray.  Current Status and Status Trend tracks the current and historical status of the Workstream.