For outdoor plants I mulch with a nice thick layer of compost covered by grass clippings. The grass clippings will fade to a light tan and help reflect light and heat keeping the mulch layer cooler and protecting the microbes from UV radiation.
Just don't use clippings from a lawn that's been sprayed with weed killer, obviously. And you can use them even without the compost layer if you don't have any. Just be sure to wet the ground before applying since the mulch since it will tend to lock in whatever environment you have before applying as it'll take an awful lot of rain to penetrate the mulch layer.