Besides the natural color that bark mulch usually comes in, it can also be purchased in a few decorative colors. Black or red are the most common. And while it can really add a lot of character to some yards and landscapes, there are a few thing you may want to consider before you place it in your flower beds.
As with natural bark mulch, colored bark will lose its color and fade. In the case of black mulch, it will also show white hard water deposits from sprinkler systems very quickly. There are, however, a few companies that make a dye specifically for re-coloring decorative bark. There's even a dye for natural colored mulch.
So besides replenishing the bark every year as you do with all mulches, you'll need to re-color it as well. You'll need to be careful not to get it on sidewalks or driveways.
Keep in mind that black decorative mulch attracts heat. And so will cause the ground and root zone to be warmer than normal. It can actually cause the soil to reach very high temperatures in hot areas.