Indicator: An indicator is a chemical compound which gives a colour change according to the pH of the given solution.

Common Indicator	Colour change
	Neutral	Acidic	Alkaline
Litmus	Purple	Red	Blue
Methyl orange	Orange	Pink	Yellow
Phenolphthalein	Colourless	Colourless	Pink
Phenilphthalein (alkaline)	Pink	Colourless	Pink

Universal indicator: A mixture of indicators which indicates the strength of the acidic or alkaline solution.