SysColorSampler is a small tool that lists all constants that define win32 colors for the current theme. You pass these constants to calls such as GetSysColor() to get the color of the display element in the current theme. A picture says more than 1000 words, so here you go:

For download, click here (48 kb). The link points to a zip file that contains a working executable, and the source code (with Visual Studio .Net 2003 solution). I haven't decided on a license yet, but there's more wizard-generated code in there than handwritten code, so I doubt you'll find much that would take more than 10 minutes to write yourself :) I'd appreciate it though if you'd send me a quick email to let me know that you use it.