I'm setting up a "tasks" spreadsheet and using condition formatting to
alert missed dates. This is a simple formula, but I'm still struggling.
If I use the formula below for past due tasks, all cells appear red
except those due today and in the future. How do I write the formula
for Condition 3 so I'm not highlighting empty cells?

Condition 1: =$D4=TODAY() [green cell]


Condition 2: =$B4="Closed" [grey cell]


Condition 3: =$D4<TODAY() [red cell]