I'm not sure where to put this question.

I work for a fire department.  We have three shifts.  Every year, I make up
a 12 month calendar and go through and change the colors of the dates to 3
colors (they work 24 on, 48 off, so one color for each shift).  Is there ANY
way to do this easier?  It seems like there should be a way to run a small
program within Word to have it color them since the formula (day 1 blue, day
2 red, day 3 green, day 4 blue, etc.) seems simple enough.  

Bonnie