function ContrastingColor(const AColor: TColor): TColor;
{ Return contracting color of the passed color. }
begin
  if ((AColor and $FF) * 77 + ((AColor shr 8) and $FF) * 150 +
    ((AColor shr 16) and $FF) * 29) > 127 * 256 then
    Result := clBlack
  else
    Result := clWhite;
end;

function GetContrastingColor(AColor: TColor): TColor;
{ Get a contrasting color. }
begin
  AColor := ColorToRGB(AColor); { convert system-defined colors }
  Result := (AColor + $000080) and $0000FF + { red component }
    (AColor + $008000) and $00FF00 + { green component }
    (AColor + $800000) and $FF0000; { blue component }
end;

function GetContrastColor(AColor: TColor): TColor;
{ Get contrast color. }
begin
  AColor := ColorToRGB(AColor); { convert system-defined colors }
  if (AColor + AColor shr 8 + AColor shr 16) and $0000FF >= $180 then
    Result := clBlack
  else
    Result := clWhite;
end;