If you select a Feature Control Frame (FCF) command in the Edit window, and that command uses a datum reference frame, PC-DMIS displays a blue and yellow trihedron to represent the reference frame for your FCF. This differs from the red and green trihedron used to represent your part's current alignment.
The following image shows:
The alignment's trihedron in red, green, and blue
The FCF's trihedron in blue and yellow
FCF Trihedron (below) and Alignment Trihedron (above)