Here is a tutorial on how to convert to Grayscale:
http://www.codersource.net/MicrosoftNet/CImageProcessing/TutorialonConvertingImagestoGrayscale.aspx[
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Just be aware that a black/white image with only 2 colors will never be anything but that, even as a grayscale image. You can't add colors that aren't there from the beginning (well, perhaps if you use some kind of interpolation, but I've never heard of that).
It's like taking an image with a low resolution and try to make the resolution higher. You can do that, but the image won't get a better quality because of that.