Change Fill Color Based On Value

I have found several good examples on how to modify the color of a field based on a value but am not having luck implementing.  My form is an evaluation with 3 sections of test scores, the total of all 3 could have a max value of 100.  Sections 1 & 2 are auto calculated, and section 3 is a value the user will input based on their review of all comments, scores, etc.  The final score has a rating, Outstanding 90-100, Satisfactory 70 - 89, and Unsatisfactory <=70.   Right now I'm not so much concerned about the color numbers, but I'm not able to get the colors to change at all.  Because this field is calculated based on sections 1-3, I put the code on its change event.  Once the user enters the final manual score in section 3, the value automatically changes.  I've also tried the exit event of the section 3 manual score, and obviously do not have either the code or where to place it right.  Below is the code I'm using, and would appreciate any help.  If I can learn how to do the 90-100, hopefully I can apply same method, different color to 70-89 and under 70.  What am I doing wrong?  Thank you.