Using the Gimp, how do I photoshop a pic so that all is black and white except a section of the pic?

I'm photoshoping this pic of me in which I have a skull on my t-shirt and I want all to be black and white and I want the skull to be red...how do I do that?Using the Gimp, how do I photoshop a pic so that all is black and white except a section of the pic?
That is called Selective Colorization.





Here are two good tutorials:


http://www.youtube.com/watch?v=XJDS-N0Zk鈥?/a>





http://www.gimp.org/tutorials/Selective_鈥?/a>