originalIM_River = imread('fig_lista4_2.bmp');
figure,title('Original image'),imshow(originalIM_River)

imRGB_River = cat(3, originalIM_River, originalIM_River, originalIM_River);
[nLine, nColumn] = size(imRGB_River);

for i = 1 : nLine
    for j = 1 : nColumn
        if imRGB_River(i,j) >= 0 && imRGB_River(i,j) <= 48
            imRGB_River(i,j,:) = [255,255,0]; % (255,255,0) is yellow
        end
    end
end

figure, title('New imagem - River painted with yellow'),imshow(imRGB_River)