For the spots, try to find sprinkles and use only the dark ones for the spots. You can also find chocolate sprinkles. You will need a pair of tweezers to do this. Or you can go to a craft store like A.C. Moore, JoAnne's, or to another in your area and get gel food coloring. Mix some frosting and using the coloring chart, color it to the color you want. Or you can Google the chart.
How To Color Icing
Wilton is the first place I go to for cake and frosting information. I also like their coloring gels. they give a richer color than what you buy at the grocery store. Craft stores sell them. Good luck and let us know how you make out.
Welcome to DC. You are going to have a lot of fun here.