I've owned a 987 base and I think the black gauges are actually superior to the grayish gauges on my current S both aesthetically (subjective) and even more so, functionally. Particularly, at night. I don't think these gauges are available after-market, yet, so I assume you're going to a dealer?
I found a couple of sites that sell them. I have spoke to one and the gauge is not a Porsche part therefore that one is out. I will not do it unless it is a genuine Porsche part.
Dont think you can change the gauge colours unless you order the special option cluster which is going to be more than the 2000 USD price for the standard cluster. Fitting the replacement gauge faces from Reap automotive here in the Uk may be your only option. REAP originally supplied the gauge faces for the UK cars for the 996 model i beleive so can offer authentic font and perfect fit at porsche quality.