Naysen, how artistic are you? You could use less paint and achieve a faux granite effect if you put on light layers and used two or three colors, say, light grey and beige sprays, holding the can further away so you retain some white background. I think they do make fake textured paints, but I suspect they are for indoors and probably cost more than you'd want to pay for this project. I would also spray the top four inches or so of the inside, so you don't see the glaring white rim above the soil.
Or, you could use masking tape and newspaper to define a few different width concentric circles around your pot, and just do a stencil effect with green paint, leaving most of the pot white.
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Dee
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