Answer: The solution turns more intense pink.
Explanation:
In NH4OH, a delicate ammonia/ammonium equilibrium is set up as shown
NH4+. + OH-<----> NH3 +. H2O
As the concentration of NH4OH increases, the solution turns more intense pink since the equilibrium shifts towards the right and phenolphthalein moves towards the ionized form as more ammonia is produced from the equilibrium above making the solution more basic. The equilibrium shifts for phenolphthalein is shown in the image attached.