No sew setting (which specifies that a thread color will not be embroidered) can be applied to a part of the pattern with a specific color.
Touch
in the embroidering edit screen.

From the thread color sequence display, select the thread color that will not be embroidered.

Touch
.
appears to indicate that the selected thread color will not be embroidered. 
.If necessary, repeat steps 2 and 3 for all thread colors that will not be embroidered.
After specifying the desired settings, touch [OK].
Touch
and then touch
to check an enlarged image of the finished embroidery.
After deselecting a region, check the image to be sure no previously hidden stitches are visible.