I typically rely on just line work in my sketchbooks...but I've been having a lot of fun adding some burgundy Prismacolor values to the sketches. Some people have asked me what I use for the white areas -  it's just white paint bucket in Photoshop. It helps the drawing 'pop' a little and it makes the line work stand out more. This was a quick self-portrait before lunch time. I don't get out much as I'm stuck in the studio pretty much 24-7, so it's getting a bit old drawing my apartment and doing self portraits. :)