Only Black works as Transparent color

[Nightmare_82]

I have the following code to set the TransparentColor of an image :

        if p_bTransparent then
        begin
        	m_oImageList.Images[Result].TransparentColor:= m_oImageList.Images[Result].Pixels[0,0,0];
        end;

But it only works with images that have the transparent color black.
Can you give me an example how to do this with other colors without the VTD-Tool?