I had a blue slate tom over a bourbon red hen. They come out all sorts of colors. I had some blue ones come out with red flecking and bluish-red banding on the tail, some with blue overlaid by light red with blue banding, some came out finely mottled bronze with dark beige banding on the body feathers, and some nicely marked bronze. Hens bred back to the tom produced black with white mottling, blue slate, blue-red, and bronze.
Here's my favorite photo of the tom with his offspring: