Colour palette

I would like to plot a 2D histogram in black and white. I define my colour palette as follows

Int_t Color[9] = {10, 19, 18, 17, 16, 15, 14, 13, 12};
gStyle->SetPalette(9, Color);

however I would like to have more gray values (more then 9). Is there any possibility to use the values in between this defined values (for example 18.5 or so)…
thank you very much
and best regards

See this example: … or-palette
to get grey it is enough to define Red Green and Blue value equal for each color limits.