如何使Node.js graphicsmagick色彩还原工作？

I am in a cloud9 environment on c9.io and I have sucessfully installed graphicsmagick and the node.js gm module. I have been successful in calling a number of methods however some I have not. One specific one I am having a problem with is the color reduction method (colors). I am in a cloud9 environment on c9.io and I hav