Indicators and their colours in acid and alkaline solution

• An indicator is substances that have distinctly different colors in acidic and basic media. Many indicators are dyes which have been extracted from natural sources, for example litmus. 
• Methyl orange, a common indicator used in titrations is pink in an acid solution but changes to show a yellow colour in an alkaline solution. 
• Phenolphthalein is pale-yellow crystals; soluble in alcohol, ether, and alkalis, insoluble in water; used as an acid-base indicator (carmine-colored to alkalis, colorless to acids) for titrations.