The reason they're coloured like that is that you can get to the pale red (0%-3%) by putting you money is much safer vehicles like term deposits or bonds. If you're getting less than 3% out, stocks aren't worth it.
In any case I would love to see (or make myself) the comparison with other vehicles.
Say use all my money to buy a long term bond today. If inflation would rise tomorrow, you correctly point out that bond yields of tomorrow's bonds will rise. However, mine is fixed. This means I'm hit, firstly, by the inflation, and secondly, by the fact that the price of the bond will fall. (The price will fall because competing bonds will have better yields tomorrow).
Correct me if I'm wrong.
http://www.bloomberg.com/news/2010-10-25/treasury-draws-nega...