To increase the number of red (H3O+) and blue (A) particles in the equilibrium solution, you could adjust the settings of the simulation by adding a stronger acid or increasing the concentration of the acid in the solution. By doing so, the dissociation of the acid would produce more H3O+ ions, while the blue particles (A) would represent the conjugate base or dissociated base particles, which would also increase as more acid dissociates.
This increase in H3O+ ions would lead to a decrease in the pH of the solution, making it more acidic. In acidic solutions, the pH value is inversely related to the concentration of H3O+; thus, a higher concentration of H3O+ ions results in a lower pH.