Highlight the cell you’re wanting to format and then click on conditional formatting. You’ll get several rule types and the one I’d use is “Format only cells that contain”. Then you’ll see three drop-down boxes. Amend the first two so they read “Cell value” and “equal to” then in the third one type N/A. Click on the format button next to the preview box. You’ll then get the format options, click on the “Fill” in the top left hand corner and then you get an array of colours to choose from. Pick an appropriate colour and then click on “OK”. Repeat the steps two more times replacing the N/A with yes and then no. You should then get the formatting you’re wanting.