The color and window sizing are defined by the shortcut LNK file. I think I found a way that will do what you need, try this:
explorer.exe "Windows PowerShell.lnk"
The LNK file is in the all user start menu which is located in different places depending whether your on XP or Windows 7. In 7 the LNK file is here:
C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories\Windows PowerShell