Black, or course...
I'm building one for my wife shortly, and the desktop box will be the following:
$39.99 - Athena Power CA Silver / Black / MicroATX Slim Desktop Computer Case 300W Power Supply
$39.99 - HITACHI 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive
$43.99 - Foxconn M61PMP-K AM3 NVIDIA MCP61P Micro ATX AMD Motherboard
$74.99 - GeIL 4GB (2 x 2GB) 240-Pin DDR3 1333 (PC3 10660) Dual Channel Kit
$88.99 - AMD Phenom II X3 740 Black Edition Heka 3.0GHz Socket AM3 95W Triple-Core
$16.99 - SAMSUNG CD/DVD Burner Black SATA Model SH-S223C - OEM
$15.80 - Shipping
$320.74 - Total
It will be about 1/2 the power of my drafting box, but about 10-15x the power of what she has. I have a Win 7 Pro OEM disk, which I think was $69. And I already have 1600x1050 Monitor, keyboard and mouse. I expect I'll have to pay for a couple of internal cables (USB to front, and CD audio cable).
If I were to re-use her case, I could knock off $40 and $10 shipping. If I re-use her Hard Disk & DVD drive (giving up SATA), then I'd save another ~$60.