Recently, two types of TiO₂ nanotube arrays (NTAs) (blue- and black-colored TiO₂ NTAs), which are easily fabricated by electrochemical self-doping, have gained much attention due particularly to their enhanced capacitive and oxidant-generating properties. These enhanced electrochemical properties mean that they have potential as basic materials for energy and environmental applications, such as in supercapacitors and anodes for water treatment. However, the understanding of the effect of the doping level of these TiO₂ NTAs on their electrochemical properties is limited because there is no direct comparison or relevant discussion of their respective electrochemical properties under the same conditions, despite the similar surface characteristics of the TiO₂ NTAs obtained by comparable electrochemical doping. Therefore, the objective of this study was to investigate the effect of the doping level of blue and black TiO₂ NTAs on their electrochemical properties, including the capacitive and oxidant-generating properties. Although no significant difference in their surface properties was found using SEM, XRD and XPS, the black TiO₂ NTA revealed a slightly higher doping level than the blue TiO₂ NTA, which is caused by the order of the electrochemical self-doping and annealing conditions. With the different doping levels of the two TiO₂ NTAs, the black TiO₂ NTA showed a higher areal capacitance, indicating good capacitive properties, and better service life in oxidant-generation than that of the blue TiO₂ NTA. The blue TiO₂ NTA exhibited a larger oxygen evolution overpotential and higher chlorine evolution efficiency than that of the black TiO₂ NTA. We report that the new knowledge on blue and black TiO₂ NTAs from this study can contribute to the further development of supercapacitors and oxidant-generating anodes for water treatment.