Today I went with a light neutral color and a dark red DMC embroidery floss.
I kept the free-hand embroidery centered.
I learned an important lesson with the blue square with red DMC floss. I stayed away from the seam line, but allowed enough space for the seam fold. This block will not have that problem I encountered in Piece No. 2.
Here is Day Three: Postage Stamp Piece No. 3

1.5 inch (3.8 cm) square of 100% cotton fabric with dark red DMC embroidery floss while maintaining 1/4 inch (0.6 cm) seam allowance.
I also wanted to include the heart block I finished on Day 2.

3-inch heart block allows a 1/4 inch (0.6 cm) seam. Finished block will be 2.5 inches square. White pattern fabric is leftover from another project. The blue floral fabric is from a scrap in the stash made up of fabric from several estate sales.