Diagram of [g − r] vs. [r − i]. The blue dots represent the points of the 2019 outburst. The green symbols indicate the points of the 2005 and 2015 outbursts (V < 16.5, crosses and open squares), while red symbols indicate the colors of the subsequent quiescence phases (V ≥ 16.5). Transformation equations between Johnson–Cousins and Sloan photometric systems have been applied. The continuous line indicates the locus of 400−600 Myr young stars (Kraus & Hillenbrand 2007). The black arrow denotes the extinction vector for A_V = 1 mag, adopting the Cardelli et al. (1989) extinction law.