The benefits of using a red-colored mulch in landscaping are mostly aesthetic, as the dyes used to color the natural color of most mulches do not provide a significant improvement to the soil's condition. Mulch, in general, is an efficient way to help preserve a gardener's desired landscape by preventing unwanted vegetation from surfacing while retaining moisture in the soil.
Red mulch is often used to complement the color scheme of a particular landscape, especially one with a lot of color and variety.
Landscaping mulches come in a variety of colors, but the most popular dye colors are red and black. Many red mulches are dyed with iron oxide, also known as rust. The additive does not cause chemical harm to vegetation, but it has been known to dye landscaping features such as concrete when the dye leeches from the mulch after a rainfall. Black mulch is processed with carbon-based dyes, which are also basically harmless to a garden or lawn.
Some mulch manufacturers may use a toxic chemical in the dying process, making it important to research products and their manufacturing processes before purchasing them. Pre-treated wood or reclaimed wood may contain certain toxins that have drained into soil, so they may potentially cause damage to vegetation. DoItYourself.com recommends verifying that the manufacturer has used raw wood for its mulch.