How to draw colored figure on monochrome bitmap (C++ Builder)

[Daniyarius]

Dear people, please help with one problem solution! THE TASK: draw a colored figure (say, a line) over monochrome image loaded from file. I cannot invent nothing but following:

TImage *Image1;
...

Image1->Picture->LoadFromFile("monochrome.bmp");
Image1->Picture->Bitmap->Canvas->Pen->Color = clBlue;
Image1->Picture->Bitmap->Canvas->LineTo(100, 100);

...

THE PROBLEM: the line is always gray, independently on chosen color.

Image1->Picture->Bitmap->Monochrome = false - does not help.