Originally Posted by Wharbone

You can buy them from day 694-700. I unfortunatley started on one of the last days, and wasn't able to buy the last one because the week changed.

The cars are:
1.Toyota GT One Race Car
2.Mazda 787B
3.Nissan R390 Race Car
4.Nissan R92CP Race Car

I think they have slightly more HP and are lighter than their colored counterpart, but I may be wrong.

I also read you can also get the following black cars from days 694-700:
5.Honda S2000
6.Clio Sport V6 24V Race Car

I am unsure of these though. I just found out about them.