2:28 describe the use of litmus, phenolphthalein and methyl orange to distinguish between acidic and alkaline solutions

Indicators are substances which change colour in response to a change in pH (acid or alkali).

IndicatorColour in acidic solution [H+]Colour in alkaline solution [OH-]
LitmusRedBlue
Methyl orangeRedYellow
PhenolphthaleinColourlessPink

Methyl orange is orange in a neutral solution