Cell A1 should always be conditionally formatted

Hi,

I'm trying to format cell A1 in my workbook so that it is always colored green. I need this because I'm creating a shared workbook and I need/want this cell colored green so that the use knows to paste all info into this cell only. I've tried conditional formatting but when I close/reopen the workbook, the cell does not remain colored. Any info will help! Thank you!