Answer: pink to colourless
Explanation:
In the ammonium hydroxide solution, the phenolphthalein will exist in its anion form due to the OH- concentration this has a pink colour. As ammonium chloride is added, the ammonium ion concentration increases far beyond the hydroxide ion concentration. The ammonium ions donate protons to the anionic form of phenolphthalein and the colour changes to colourless. The equilibrium involved is shown in the image attached.