If you are applying a colormap to the base color of the object, this color change will affect all active parameters of the surface: ambient, diffuse, specular, reflectivity, and transparency. i.e. a red texture color will make reflections red along with the diffuse and ambient (if the object was reflective). The solution to prevent this from happening, if it is not desired, is to create a white (or other solid color) texture map and texture that to the reflective color, or other surface parameter you want to be independant of color. The texture doesn't have to
be big.
Caveats -- Renderman does not work the same way. Also, remember its transparency color, not opacity, so white is transparent unless you check the "invert transparency" box.
