Patio slab just outside sliding doors.
Can a stencil be used on an already painted concrete patio slab?
Paint/stencil must stand up to Arizona heat.
https://www.concretenetwork.com/concrete-stencils/stenciling-process.html
You really should power off the first paint if you can. Clean well then prime & Paint. I live in Las Vegas and I notice that east or north patios hold up much better than west or south facing patios. My front courtyard faces west and I finally gave up on the painted surface and put in outdoor tile to cover the ugly thing.