Use ColorSort 
to reduce the embroidery to the minimum number of color blocks. The final number of color blocks produced in the ColorSort process can vary, depending on any overlap between areas, or whether thread effects are used. If possible, it leaves only one color block for each thread color used. If necessary, trims are added to connect the areas that use the same thread color. Unnecessary Color Change commands are removed.
Alternatively, you can use the ColorSort option in Export 
to merge your color blocks when creating an embroidery file for stitching out.
ColorSort affects the whole of the embroidery, even if only part of it is visible. All stitches in the embroidery will be shown when the ColorSort is complete.
If desired, click Undo to return to the original colors.
Shortcuts
-
Tools, Home Tab:
-
Keys: Alt, H, CL