Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

procedure EdBackColor(FontC: TColor; var EditableColor,
   ReadOnlyColor: TColor);
   // Calculate the luminance of the color using the simplified formula 
  //     luminance = 0.25*red + 0.625*green + 0.125*blue 
  // If greater than 0.5, use a dark background 
var
   R, G, B: Integer;
 begin
   R := GetRValue(FontC) * 2;
   G := GetGValue(FontC) * 5;
   B := GetBValue(FontC);
   if R + G + B < 1024 then
   begin
     EditableColor := clWhite;
     ReadOnlyColor := clSilver;
   end
   else
   begin
     EditableColor := clBlack;
     ReadOnlyColor := clDkGray;
   end;
 end;