The Sky color is actually a white tinted with a little blue. You'll see it when the dot on the can dries. The color off of the wall will look different depending on the amount of light hitting it.
I never liked the obvious robin egg blues or darker colors that looked unnatural. The sky is tough color mimic. I hope you like it. if anything, you'll want more blue at first.
I got away from Behr and went to SW commercial lines. ( a commercial store is not too far from me.) I get better smoothness and more mileage.
Make a 100" x 117" table (tool box) and move the whole plan B (yours) on to it. I wasn't trying to upset the applecart.
The access hatch can have a shed on top of it. Just supply track feeders to the hatch track. You can cut a track in half for the seam.