Usually they list somewhere on there website what lighting they use. If not you could ask or tell what you have. Mh's are commonly used and you'll probably see the K (color temperature) and maybe wattage.
If the lighting is not listed, I would definitly send a message to ask....there are many sellers out there that use lighting to their benefit.
If you are really worried about what your seeing, being what you get- ask for a camera shot w/ flash. This will give you an idea of what you "could" be getting.
If you have never seen your corals w/ a flash shot- try it, and you will understand. A must experiance, with a large variety of corals. It will help you alot in the long run. Try it, understand it, and learn from it.
I've used a flash and more so then not the corals look like ****-it's all about the lighting as to how they look. That and a good photo imaging program :/