Reduce color of a bitmap

[Betschart Linus]

Hello friends,

I want to reduce the color depth of a bitmap.

I read here: http://www.dotnet247.com/247referenc...29/147842.aspx that
it's just possible with GIF Files, but I am not quiet sure about this
statement, because, if i use this sample code:
http://support.microsoft.com/?id=319061 (but save as BMP and not as GIF), it
works!
My problem now is, that it saves just in grayscale, not in colour!
Can anyone help me?

thx a lot in advance
LB
PS: the I started the same question in ...dotnet.framework.drawing, but
because I'm not quiet sure where I should post it, I do it also here