Folks get confused when it comes to mulch. Mulch is both a noun and a verb. Mulch as a verb means to cover the soil in order to reduce evaporation and maintain the moisture content of the soil, to reduce erosion and help maintain soil temperature so it doesn't get too hot or too cold. Mulch as a noun covers a lot of things. Mulch can be everything from shredded paper and plastic to rocks and gravel. Mostly though mulch is made from once living plant material and this can be from trees, from tree bark, from brush, even leaves and grass clippings. Mulch can be large, such as pine bark mulch, or it can be small such as hardwood chips. It all depends on how it was processed. Some mulches last a long time such as hardwood mulches like oak, while other softwoods such as hackberry and pine decompose much quicker. All mulches sooner or later turn into compost. Usually bagged mulches will state whether it is hardwood or softwood and usually the hardwood mulches cost more. Hardwood mulches also, after they decompose, provide more long term nutrients than do softwoods. One has to determine what his long term goal is as to what mulch to use. Is it to build up the soil over time or just to use cosmetically? If you primary concern is cosmetics then use the inexpensive pine bark or softwood mulches. If for long term, such as in a permanent garden, use the finer processed small particle hardwood mulches. Most colored mulches are just for cosmetics and normally made from pine and pine bark or other softwood.
