shading and cmyk colors will produce wrong output colors

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Use a graphics like a logo with a dominant cmyk color
2. Use the same cmyk color for headerColorOne
3. Use some shaded header option (headershade=shade-lr)

What is the expected output? What do you see instead?
Color of Logo and and header should be exactly the same. Instead the colors are 
different, depending on the actual choice of colors.

I think the reason for this problem is the fact that the tikz "\shade"-command 
does ONLY allow for rgb. 
(http://groups.google.com/group/comp.text.tex/browse_thread/thread/768fe172b0033
4e9) Every cmyk color is automatically converted to rgb when using shading, so 
the header-boxes will be in rgb and will never be the same color anymore.

My "solution" was to change everything (inkluding the logos) to rgb, of cause 
also changing the cls to the rgb option. Then at least logo and header boxes 
have the same (wrong) color.

Original issue reported on code.google.com by [email protected] on 10 Feb 2012 at 2:54