Hello,
Sometimes the manufacturers of these kits make mistakes and can either miss a color or not give enough of a certain color. All you have to do is contact the manufacturer of the kit, which I think is MCG and let them know the issue and they should just send you out some yarn for their product. Here is the link to contact them:
http://www.mcgtextiles.com/
The number should be located in the upper right hand corner of their website.
Hope this helps :) Thank you!
~Kristi @ ECS