B = imread('Images\spamResource\spamplain1.jpg','jpg');
[x,y,q] = size(B);
for i = 1:1:x,
  for j = 1:1:y,
    if B(i,j,1) < 40
        if B(i,j,2) < 80
            B(i,j,:) = [0,255,0];
        end
    end
  end
end

% This seems to work well for the particular image spamplain1.jpg
% But it will identify many blacks as blue.  Black often looks
% like blue to us humans too, though!