I am severely color-blind, as many people know. Here’s a test for you.
I’m told there are numbers in those pictures. I can see a 9 in the top left corner, but nothing else.
This one has a 37, which I could make-out after I was told what where in was (by Eye Pilot). Is it subtle for you, too?
If you have a Mac, you can download Color Oracle and see what it’s like for color blind people to look at your computer. (If you’re running something else, try Color Doctor.) Just for shits and giggles, I used Oracle. I didn’t learn anything. FYI, I’ve got some deuteranopia and some protanopia. Neither of which explain my problems with blue and purple. I guess that’s a mystery yet to be solved. Anyway …