Colour cell

[stete]

Hello!i want to see how many days a failure lasts. i have a start date and an end date. when a failure occures and is repaired the cell becomes green. i want the cell to be red when i have a start date but it hasn t be repaired yet. i tried to do it with conditional formatting but i have to do it seperately for every cell and it is very time consuming (see the last row). there is an other way to do it?
thank you in advance