Acacia is a rich source of tannins, so a mordant is not necessarily needed, and often, acacia is dyed with iron to create grays and blacks, or it can be overdyed with indigo for muted greens.

Acacia dyed without the addition of iron, results in beige colors with a pink tone to them, and I’ve seen more of this pinkish tone on cellulose fibers. To obtain blacks with Acacia, dye with Logwood and iron.  Logwood has long been a necessary natural dye for achieving true blacks, especially for Victorian mourning clothing. 

Cochineal can be dyed with tannins and an acid instead of the fibers being premordanted with alum.  So, Acacia makes a great source of tannin to dye with a bit of cochineal for some peachy pinks.  Historically, Cochineal was dyed with tannin containing leaves and citrus for the acid, and renowned natural dyers have said that the lightfastness of fabrics dyed this way, are as lightfast or more lightfast than fabrics that were alum mordanted.

Acacia is a good source of tannins and has been used by the tanning industry, but the plants/trees are very widely useful and many different parts are used for a variety of uses. 

Acacia is a large genus of shrubs and trees and are commonly referred to as wattles or acacias.  They grow in Africa, Brazil, India, China and Australia.