Hi Lionel
I have not done it yet, but plan to do something similar in the near future. I would suggest getting a config file (excel table for example and let's call it Targets for now) with a column for Month, RedValue and BlueValue. For each month you can then set these values and associate the Targets table with the dates of the sales table.
In QS KPI object, you can then go to Appearance -> Color -> Conditional Colors ON -> Library Colors OFF -> and add two limits. The first limit will be something like Sum(Targets.RedValue) and the second will be something like Sum(Targets.BlueValue). Your colours between the limits will then be red, blue and green (from left to right) and will then filter as you filter your months.
Regards,
Mauritz