What colour does methyl orange show in an acidic solution?

Correct answer: Red

Methyl orange is an acid–base indicator whose colour depends on the solution’s pH. In an acidic solution it appears red; as the medium becomes less acidic and then basic, it changes through orange toward yellow. Therefore option B is correct. Yellow is associated with the basic side of its transition, whereas green and blue are not the expected methyl-orange colours in this test.