Originally Posted by Tideland Prius

it's just for easy reference when you glance at the screen.

Green - 7 or 8 bars
blue - 3-6 bars. Should be easy to read since half battery is 4 so is it -1 or +1 or +2 bars from half
pink (or purple) - 1-2 bars

Again, it's just there so that you don't have to count the bars. A quick glance and you should know how many bars you have.