Painting planter pots are one of my favourite projects to do in between other major projects. There is no pressure with getting them done and gives me a break to take a breather and just play with more simple designs.
Posca and Artistro paint pens are my ideal tools of choice, as they stay on both plastic and terracotta and remain vibrant. Using a base layer of clear gesso prevents the paint to soak into the terracotta, so less paint is required with no need to coat with multiple layers.
Giving extra personality to a plant with its own unique pot is so fun! Some of my earlier pot creations I used patio acrylic paints but found they would bubble from the water trying to seep through during watering. There has been no issue with the paint markers.
I highly recommend painting on pots for something fun, quick and adding a unique flare to your home!