Black and White.

Its one of those mediums that can be both a pain and a joy to work with. For most people, black and white is simply desaturating the picture to zero, but theres much more to black and white than that. In film photography black ans white film reacts differently to different colors meaning that if you took the exact same scene with both color and black and white film, desaturated the color film and printed them both out in black and white the images would look quite different. The reason for this is that the black and white film will expose faster or slower to different wavelengths of light, so your yellow might expose fast while the blue will expose slower giving you a higher contrast between blue and yellow than you would in color film. If you want more check out this site on converting color photos to black and white, as it explains it much better than I could myself.

Paul