Polished ice, like water, tends to "pipe" light and create a sort of fiber optic, internal reflection effect. Using that, you can probably get the sculptures to glow in various colours by bringing an illumination source in contact with them. The illumination can be gelled, of course. The effect of glowing from within should create more of an eye-catching effect than illuminating from outside (e.g. with a flash), which will proably just give specular highlights and surface reflections.
If you can speak to the sculptors in advance, perhaps you could get them to make a recess in the bottom or side of their work, into which a light source could be fed.