Colour coding

Hi
I'm trying to compare two columns, target and current grade using our schools grading system of 1-,1=,1+, 2-,2=,2+ etc and colour code them.
We use green for on target, orange if they're one grade below and red if they are two grades below, so the default colour coding doesn't work.
I have figured out how to assign colours to values in the grade editor, but when I do the calculation, the lowest figure is too low for me to assign a colour to (it doesn't appear on the slides scale) .
In the screenshot, I need 0 to be green, -0.4 to be orange and -0.7 to be red, but cannot change anything below -0.1. When I change the value range to something lower, it changes the original values to have the same problem!!
Help?!!

Hi TillyC,
Send us an e-mail from the app: Help > Support&Suggestions and we'll send you a link to an updated version that will let you assign any value in the colour configuration.

Regards