the color varies from rock to rock, Most people like their rock to have more purple than any other color. The more coraline algea "purple" you have on your rock the better your tank looks. But dont go out and start puming chemicals in your tank. that comes with time. Jay started with dry rock wich is also a good way to start, that way you dont introduce any unwanted pesky critters.
Good job your tank is looking good. I dont see bubbles in your skimmer though. is it on?:thumbsup::thumbsup: