Conditional Formatting of date cells

I have a list of physical exams done by people. These exams need to be updated yearly. I need to see when their next exam is upcoming, 30, 60, and 90 days out. I'm trying to do this with conditional formatting, but am having problems with the formula. Is this the best/easiest way to do this?

The formulas that I found are such:

=(D3-today() )<30 - (format as red)
=(D3-today() )<60 - (format as orange)
=(D3-today() )<90 - (format as yellow)

The problem I'm having is that no matter which order I put them in, all the cells turn that color.

Unfortunately I can't upload a working copy of the spreadsheet.