MAPT and red-green color blindness: [18F]flortaucipir enabled monitoring of tau spread and disease progression in AD (example in Figure 2A; Vogel et al., 2020; Chen et al., 2021); however, it does not detect primary tauopathies such as PSP and CBD (Fleisher et al., 2020; Malpetti et al., 2021; Van Wambeke et al., 2021).