In case your wondering "Whats up with all the oatmeal Danika?", we eat a freakish amount in our house, and I have a kid with food allergies and gluten issues so I have to have a gluten-free version as well.
Here is how to paint your planter to look like weathered stone...
Mix some primer with a few drops of black and thin with a bit of water.
Paint one coat one and an inch or two inside the rim. Let dry. Re coat if necessary. This planter is treated on the inside so its waterproof, no need to seal the inside.
Once dry add a few drops more white primer to your mix to lighten (you can also do the reverse and add black is you want a darker look). Brush a thin coat over the pot.
Quickly sponge most of it off with a clean damp sponge. Let dry.
You can seal with a flat varnish for added protection if it will be exposed to the elements, but mine is staying indoors.