A brick's color can be attributed to its clay composition, any added compounds, its firing temperature and any surface treatments. Because brick is composed of naturally occurring materials, all brick will not necessarily be exactly the same. For this reason, some brick may be of a slightly different color than others in a given batch. Usually, this adds character to a wall, but occasionally it is desired to blend these brick with other brick in the wall. This can be done by individually staining the brick in question.
Staining is a common practice and is usually done by a professional with expertise in its application. The stain itself is a proprietary product made specifically for brick. A local brick supplier in your Yellow Pages should be consulted for a product and professional applicator. Since the surrounding mortar joints must be masked, it is a time consuming process and is usually only done when a limited number of brick are involved. If staining is done properly, it should have no detrimental effect on the bricks and should provide a long lasting finish.