One or more high wattage metal halides would work very well for lighting, and might be sufficient for basking as well. Species that are real heliophiles might need warmer basking temps than the metal halides can provide (while maintaining a safe distance between them and the chameleons), but for many it should work well. HPS produces orange light, which looks like hell and one would imagine would likely have some psychological repercussions for the chameleon. Metal halides of appropriate spectrum--color temp of 5500K, 6500K, or 10,000K, sometimes just called 10K--should look relatively similar to sunlight. Horticultural bulbs should work well in this regard.