Hi Danny,
Although I find the graph in the roast analyzer very readable indoors, when I am outdoors where I roast I find it very difficult to read, especially the target roast, even though I have the opacity for same turned all the way up. Knowing you, I'm sure you did a lot of trial and error to come up with the background color that you did. However, I wonder if a light background might not work better for me in high ambient light areas. I guess I could try making that curve a very light color too.
Thanks,
Kor