A pH indicator is a substance that changes color in different pH environments. A universal indicator is a mixture of pH indicators that form a continuous spectrum of colors at different pH values. The most common indicators are
Red at pH < 4.4. Yellow at pH > 6.2.
Yellow at pH < 6. Blue at pH > 7.6.
Orange at pH < 0. Colorless at pH 0 to 8.2. Fuschia at pH 8.2 to 12. Colorless at pH > 13.
Red at pH < 1.4. Yellow at pH > 2.8 and pH < 8. Blue at pH > 9.6.
Red at low pH. Green at neutral pH. Blue-violet at high pH.