How to change colours in a 16 colour bitmap

Problem/Question/Abstract:

How to change colors in a 16 colour bitmap

Answer:

I found the solution which works best, although the final version will have the colors computed rather than hard coded. The bitmap I am using actually only uses the first 4 colors in the palette for shades of grey.

procedure TForm1.SetWallpaperPalette;
type
  RGBQUAD = packed record
    rgbBlue: Byte;
    rgbGreen: Byte;
    rgbRed: Byte;
    rgbReserved: Byte;
  end;
var
  NewColors: array[1..4] of RGBQUAD;
begin
  FillChar(NewColors, SizeOf(NewColors), 0);
  with NewColors[1] do
  begin
    rgbBlue := 0;
    rgbGreen := $C6;
    rgbRed := $C6;
  end;
  with NewColors[2] do
  begin
    rgbBlue := 0;
    rgbGreen := $CE;
    rgbRed := $CE;
  end;
  with NewColors[3] do
  begin
    rgbBlue := 0;
    rgbGreen := $D6;
    rgbRed := $D6;
  end;
  with NewColors[4] do
  begin
    rgbBlue := 0;
    rgbGreen := $DE;
    rgbRed := $DE;
  end;
  if Assigned(SpeedBar1.Wallpaper.Bitmap) then
    SetDibColorTable(SpeedBar1.Wallpaper.Bitmap.Canvas.Handle, 0, 4, NewColors);
end;