conditional colours within a pie chart based on a grading system

I'm creating hundreds of pie charts based on data that will be updated monthly. The pie charts are showing 10 categories which have a final grade of either EXCLNT (green) GOOD (yellow) MODRTE (orange) POOR (pink) or UNACCPT (red). I want the colours of each segment to change to one of these colours depending on the grade they get which will be changing throughout the year......I also want the pie segments to remain equally sized. Is this possible? I am ok with Excel charts and general functions, have no experience of Macros though so if this is what's needed please give me an idiot's guide!