Wood mulch can be a variety of colors, from dark or light brown to red or black. It is usually finely-shredded and has an earthy odor to it, especially when first spread.
Wood mulch is the easiest and cheapest to install (for one installation). It also helps retain moisture in the ground so you don’t have to water as often as well as adding organic matter to the soil as it decomposes.
The color of wood contrasts well with plants and lawns, and there isn’t a need for an additional barrier between weeds or your lawn. Mulch is also soft and easy to walk on.