Monochrome Rainbow

Is a rainbow still a rainbow if it doesn't contain a multiplicity of color, or is it all about form and feeling?  I liked the color contrast in this image.  It's not garish, like an over-processed photograph of graffiti.  Rather, it's closer to one of those images where one color is highlighted against a black and white background.  But the muted colors of the background both "pop" the more colorful part of the image and preserve the background as a real part of the image.