Well Leah, I would paint the gray first, this color will cover easier then the orange. You want to paint the gray two coats then let it sit a few days to cure, then you can put painters tape in the corner along the seem and then paint your orange. I only say wait a few days cause as a pro painter I could cut the line with out tape, and if you put tape on a freshly painted wall you risk pulling it off when you pull the tape. I hope this helps. Best of luck.