What you are showing is 4x4, not 6x8. I also don't see the white in your picture. However, assuming the entire quilt is black on one side of the log cabin and white on the other with red centers, you will need the following yardages (42" width): white: 3-3/8; black 4; red 1/2. I couldn't make the same shape heart, but you could probably figure out yardages based on percentages.