I am pretty familiar with Excel, but just learning formulas...

I have two columns I am working with for this question, a due date and
completed date.

I used the formula =A1<=today() to highlight a "past due" date red. I was
wondering if in my completed date column I could enter a formula that would
highlght a date Red if it was past the date, or blue if it is bofore the due
date.

Also, will this update as I work with it, or only as I enter in cells?

Thanks for your help!