It is common to encounter wood products that diverge from wood's natural colour. These discolourations occur throughout the whole processing chain, may affect value, and raise questions from users and producers. Discolourations are generally classed as either microbial or non-microbial in origin but some are complex and involve both biotic and abiotic factors. The terminology, as well as possible methods for control and remediation, are discussed. In some cases preventive measures remain unknown, while for other discolouration types some methods may be more feasible than others, and for some an integrated approach is needed. Microbial discolourations are more commonly encountered and among these the discolouration caused by bluestain fungi are most prevalent, especially on softwoods. Since it has also been the focus of more studies, this brochure covers bluestain control in significant depth.