Customer contacted me because this 60 inch plotter was not seeing red. Kept saying either faulty or incorrect. I went there and changed the read sensor for the red and it made no change. All reds being tried were 771. Then I am researching and see red 774 listed for that model. When we went to purchase the 774, the site we were using would change it to red 771. Can someone help me understand what is going on with red.