Synthetic indicators are indicators that are made from artificial substances. Synthetic indicators include phenolphthalein and methyl orange.
When litmus papers are used to test a neutral solution, the same result (the below pictures) occurs.
Litmus papers in neutral solutions
Neutral solutions are those in which the concentrations of hydrogen and hydroxide ions are the same. Examples, sodium chloride solution, sugar solutions and water.
Phenolphthalein is colourless in an acid medium. The colour of phenolphthalein in a basic medium is pink.
Test for acid and base using phenolphthalein indicator
Image Credits: Image
Methyl orange indicator:
Methyl orange is pink in an acid medium. Methyl orange appears yellow in a basic medium.
Test for acid and base using methyl orange indicator
Colour in acid
Colour in base
Blue → Red
Red → Blue