Formula for color-coding cells

Good morning,
I am creating a spreadsheet for our inventory program where I work. The list will be by part number, and I will be setting inventory parameters to determine whether the inventory levels are Green (acceptable), Yellow (require attention) or Red (approaching critical situation).
A line item will look similar to the following --
Part Number In stock Green Level Yellow Level Red Level

I am looking for the correct verbiage for a formula that will color-code the "Part Number" cell... What I am trying to achieve is:
If quantity in "Part Number" is greater than the quantity in the "Yellow" quantity,,, then color code the cell GREEN.
If quantity in "Part Number" is greater than the "Red" quantity, but less than the "Yellow" quantity, then color code the cell YELLOW.
If quantity is equal to or less than the "Red" quantity, then color code the cell RED

Thanks, in advance, for your assistance.

Darrell