Hope the drawing is coming along well. I took a look at the lesson in the book, and it would seem to me you'd want to go with Henna, Terra Cotta, Mahogany Red or a similar earthy red color. I don't know the polychromos line, but the name Indian Red I would assume connotates an earthy red color. Here is a reference of all the Prismacolors: Prismacolor Reference
You might also want to experiment with Dahlia Purple, that would seem like it would be a nice choice as well to go with the Indigo Blue and the Scarlet Lake.
As far as coverage goes, the more layers you use with sharp pencils, the more paper will be covered. If you have just put down the first layer or two and the paper is still showing thru, for this lesson that would seem okay since you will be adding more layers to cover the paper. Just make sure to keep the pencils sharp!
Good luck and can't wait to see the progress!