Douglas, you need to use impixelinfo(), not hpimpixelinfo(). And you probably need to adjust where it is so you can see it. And you're passing in 2. I wouldn't do that. I'd just call it right after you call imshow() to make sure you're using it on the right figure.
hp = impixelinfo();
hp.Unit = 'normalized';
hp.Position = [0.01, 0.98, 0.2, 0.1]; % [xLeft, yTop, width, height]
If that doesn't show the pixel values in the upper left of your figure, then adjust the position.
To find red, see my Simple Color Detection app in my File Exchange where I do exactly that. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862
Basically you can extract the color planes
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
and, if your red is exactly (255,0,0) then find those pixels like this
redPixels = redChannel == 255 & greenChannel == 0 & blueChannel == 0;
imshow(redPixels);
To find black (0,0,0) pixels:
blackPixels = redChannel == 0 & greenChannel == 0 & blueChannel == 0;
imshow(blackPixels);
To find white (255,255,255) pixels:
whitePixels = redChannel == 255 & greenChannel == 255 & blueChannel == 255;
imshow(whitePixels);
If your colors are not pure computer graphics like that, then see my File Exchange app, or see the Color Thresholder on the Apps tab of the tool ribbon.
