Kieferschild, Good morning.
As you set a RED color, you now how to create a rule.
Now, you'll create a NEW RULE.
Select at C column the EXPIRE DATES
CF MENU --> NEW RULE --> USING FORMULA
Type it at field: =AND(C2>=TODAY(),C2-TODAY()<=15)
Choose ORANGE as fill format
Please, tell us if it working now.
Belo Horizonte, Brasil.