shade color problem

I have a problem displaying colors from my color table. When I choose 
the "shade colors" option for color-shaded plan view in order to see 
interpolated colors all colors get darker (white becomes grey etc..)
The same happens on color filled countour plan view.
Is it possible to avoid this grey effect when using interpolated views? I 
would like to have interpolation but still use my original colors from my 
color table.
Thanks for any help!

Vaclav Hornik