Answer and Explanation:
The color change of a pH indicator is caused due to the dissociation of protons H+. The most common indicators are: phenolphthalein, methyl red, and bromothymol blue, which are used to indicate pH ranges of about 8 to 10, 4.5 to 6, and 6 to 7.5, respectively. For each indicator, phenolphthalein goes from colorless to pink, methyl red goes from red to yellow, and bromothymol blue goes from yellow to blue.