In the Liebermann's nitroso reaction changes in the colour of phenol occurs as :

In Liebermann's nitroso reaction, phenol is given a blue colour by being treated with sodium nitrite in the presence of strong sulfuric acid.
The red solution is then created by diluting it with water. It turns blue after basification with dilute NaOH solution.
Brown or red-greenish red-deep blue is the new colour.