Allow a background colour to be set for custom headers

[hellweaver666]

Currently WordPress allows you to set a custom image background for the header and a custom text color but doesn't give the users a way to set a custom background color for the header.

Adding a simple color picker for the header background would give users a lot more flexibility in what they can do with the header without using external software to create graphics etc. Perhaps needs a way to activate it from the themes functions.php (suggest add_custom_header_color?)