Most of the genes and regulators of anthocyanin biosynthesis are controlled by the bZIP transcription factor, HY5. However, residual anthocyanin production is still detected in Arabidopsis hy5 mutants, suggesting there are other genes or regulators involved in anthocyanin biosynthesis independent of HY5. To investigate this further, Qiu et al. generated Slhy5 mutants of the tomato cultivar ‘Indigo Rose’ using a CRISPR/Cas9 system (see pp. 643–656), and identified several candidate HY5-dependent and -independent regulators of anthocyanin biosynthesis in tomato.