I don't think the drawing color is an option to imfreehand(). So after you've completed drawing it, you'll have to use plot() to place the outline into the overlay with the color you want.
With the newer drawfreehand() function, there is an input option to specify the color.
Kindly use the Image Segment App to draw a free hand Region of Interest (ROI) around the nucleus and create a binary mask. For performing any statistical analysis on the image, you can use this mask.
If you want to crop the free-hand ROI from the image, refer the following links
Best Answer