Electrolysis and acid and base liquid colour change

We mix cooking salt (NaCl) with water (H₂O). Then add an electric current, more than 1.23volt and the electrolysis starts. There is produced H₂ (hydrogen), O₂ (oxygen), NaOH (Sodium hydroxide) and Cl₂ (chlorine gas). We did not intend to produce chlorine gas, but luckily it was in so small amounts, that no harm was done to us. We have red cabbage as an acid – base indicator, and salt water as a neutral. After the electrolysis there is formed NaOH and the solution becomes base, which is seen by the solution turning green/yellow.