  We investigate the zero-temperature quantum phase transitions of the
disordered three-color quantum Ashkin-Teller spin chain by means of large-scale
Monte Carlo simulations. We find that the first-order phase transitions of the
clean system are rounded by the quenched disorder. For weak inter-color
coupling, the resulting emergent quantum critical point between the
paramagnetic phase and the magnetically ordered Baxter phase is of
infinite-randomness type and belongs to the universality class of the random
transverse-field Ising model, as predicted by recent strong-disorder
renormalization group calculations. We also find evidence for unconventional
critical behavior in the case of strong inter-color coupling, even though an
unequivocal determination of the universality class is beyond our numerical
capabilities. We compare our results to earlier simulations, and we discuss
implications for the classification of phase transitions in the presence of
disorder.
