procedure ChangeRGB(var Bitmap:TBitmap;R,G,B:integer);
var
H,V:integer;
DstRow:^TRGBTriple; // to jest wskaźnik dopixela
begin
 Bitmap.PixelFormat:=pf24bit;
 for V:=0 to Bitmap.Height -1 do
  begin
      DstRow:=Bitmap.ScanLine[V];
      for H:=0 to Bitmap.Width -1 do
      begin
      DstRow^:=ChangeRGBColor(DStrow^,R,G,B);
       Inc(DstRow);
     end;
  end;
end;

Funkcja zamienia wartość TColor na TRGBTriple.

function ColorToTriple(Color:TColor):TRGBTriple;
type
Rec=Record
Case TColor of
1:( ColorValue:TColor );
2:(Bytes: array [0..3] of Byte);
end;
var
Col:Rec;
begin
Col.ColorValue:= Color;

Result.rgbtRed :=Col.Bytes[0];
Result.rgbtGreen :=Col.Bytes[1];
Result.rgbtBlue :=Col.Bytes[2];
end ;

function ChangeRGBColor(color:TRGBTriple;R,G,B:integer):TRGBTriple;
begin

if  B+Color.rgbtBlue >255 then Color.rgbtBlue :=255 else
if  B+Color.rgbtBlue <0 then  Color.rgbtBlue :=0 else
inc(Color.rgbtBlue,B) ;


if  G+Color.rgbtGreen >255 then Color.rgbtGreen :=255 else
if  G+Color.rgbtGreen <0 then  Color.rgbtGreen :=0 else
inc(Color.rgbtGreen,G) ;

if  R+Color.rgbtRed >255 then Color.rgbtRed :=255 else
if  R+Color.rgbtRed <0 then  Color.rgbtRed :=0 else
inc(Color.rgbtRed,R) ;
Result:=Color;

end;