CC = contrasting color. This is used when a pattern called for a second or additional color to be changes. Contrasting Color is always a color opposite on the color wheel but in yarn pattern language it can mean a secondary color that makes the first color stand out.
Watch Mikey as he adds a second color to a granny square using a contrasting color in the video link. The contrasting color is one that is opposite the first color on the color wheel or gives a completely opposite color or light/dark value from the first yarn. The video link is cued up to the change. http://youtu.be/4x6ETtAwUrg?t=8m1s
For the complete video watch below.