A dreadlock, in essence, is a hanging lock coil of matted hair. The structure of the dreadlock Is both a blessing & a curse when it comes down to hair dye. Because this lock of hair is not processed, it creates a stronger barrier for the dye to permeate. For this reason, natural dye is that much harder to utilize.
Is the method most people turn to with dreadlocks because of its strength. Walnut powder, black tea, & Cassia (for already lightened hair) can also be utilized. Those dying with dreadlocks have to remember the vinegar rise before & after, & to get results, the process may have to be repeated several times depending on the length & porosity of hair.
Is also an option. Because of the makeup of the coil, rinses will not last as long as a permanent dye or a bleach, however, because the hair is matted, special care has to be taken to ensure all of the product is removed from the dreadlocks, especially closer to the scalp where the hair is straighter. When applying any kind of dye, always start from the front & work backwards, making sure all of the lock is covered, or if you are working on the ends only, ensure there is enough product to fully saturate the hair. Conditioning is a crucial step, as the hair will need time to adjust. Overnight would work best, or a minimum of 1 hour. A cool blow dryer will speed up drying time, however sun exposure is the preferred method.