function GetRightMostColor(var map: TIEBitmap; TRect boundRect): TColor;
type
  PByte = ^Byte;
var
  i,j,k, rightMax: Integer;
  testColor: Integer;
  whiteColor: Integer;
  inByteP:  PByte;
begin
whiteColor := 255255255;
rightMax := 0;
for i := boundRect.top to boundRect.bottom do
    begin
    inByteP := map.ScanLine[i];
    inByteP := Inc(inByteP, boundRect.right * 3); // 3 channels => RGB
    for j := boundRect.right Downto boundRect.left do
        begin         
        testColor := 0;
        // channels are actually in BGR order.
        Dec(inByteP);
        testColor := testColor + (Integer(inByteP^)shl 16); // red
        Dec(inByteP);
        testColor := testColor + (Integer(inByteP^)shl 8);  // green
        Dec(inByteP);
        testColor := testColor + Integer(inByteP^);         // blue               
        if (testColor <> whiteColor) then
           begin 
           if ( j > rightMax) then 
               rightMax := j;
           Break;  // exit j loop
           end;                 
        end;
    end;
Result = TColor(testColor);
end;

var
  TestBM: TIEBitmap;

procedure TForm2.FormCreate(Sender: TObject);
begin
  TestBM := TIEBitmap.Create;
  TestBM.Read('colors.bmp'); // above image converted to .bmp, see attached file
end;

procedure TForm2.Button1Click(Sender: TObject);
var
  TestRect: TRect;
begin
  TestRect.Left := 24;
  TestRect.Top := 117;
  TestRect.Right := 450;
  TestRect.Bottom := 214;

  GetRightMostNonWhiteColorInRectangle(TestBM, TestRect);
end;

function TForm2.GetRightMostNonWhiteColorInRectangle(const ABitmap: TIEBitmap; const ARectangle: TRect): TColor;
var
  x, y: Integer;
  px: hyiedefs.PRGB;
begin
  Result := clWhite;

  for y := ARectangle.Top to ARectangle.Bottom do // loop lines
  begin
    px := TestBM.Scanline[y];
    for x := ARectangle.Right downto ARectangle.Left do // loop pixels
    begin
      with px^ do
      begin
        if (r <> 255) and (g <> 255) and (b <> 255) then // Found NonWhite Pixel
          CodeSite.Send('x', x); // sent by all pixels regardless whether they are white or non-white!!! <<<<<<<<<<<<<<<<<<<<<<
      end;
    end;
  end;
end;

procedure TForm2.FormDestroy(Sender: TObject);
begin
  if Assigned(TestBM) then
    TestBM.Free;
end;

if (r <> 255) and (g <> 255) and (b <> 255) then

function TForm2.GetRightMostNonWhiteColorInRectangle(const ABitmap: TIEBitmap; const ARectangle: TRect): TColor;
var
  x, y: Integer;
  px: hyiedefs.PRGB;
  ThisMax: Integer;
begin
  Result := 16777215; // clWhite

  ThisMax := -1;
  for y := ARectangle.Top to ARectangle.Bottom do // loop lines
  begin
    px := TestBM.Scanline[y]; // points to first pixel in the WHOLE bitmap!
    Inc(px, ARectangle.Right); // go to the pixel of the right side of the rectangle
    for x := ARectangle.Right downto ARectangle.Left do // loop pixels down to left side of rectangle
    begin
      with px^ do // check this pixel
      begin
        if (r <> 255) or (g <> 255) or (b <> 255) then // Found NonWhite Pixel
        begin
          //CodeSite.Send('RGB(r, g, b)', RGB(r, g, b));
          if x >= ThisMax then // if this pixel is more or equal rightmost than the previous rightmost
          begin
            ThisMax := x; // store this pixel position
            Result := RGB(r, g, b);
          end;
          BREAK; // go to the next scanline
        end;
      end;
      Dec(px); // NonWhite pixel not found -> go to previous pixel
    end;
  end;
end;

for (x = boundRect.right downto boundRect.left)
    {
    for (y = boundRect.top to boundRect.bottom) 
        {
        if (color(y,x) is not white)
           return color(y,x); // done, exit the function  
        }    
    }