An indicator is a compound that is one color in basic solutions (baking soda with water), and another in acidic solutions (vinegar, which is a watered down version of an acid called acetic acid). When you added the indicator (turmeric and alcohol solution) to the base, it changed the solution's color by reacting with the hydroxide (part of the base's compound). When you added vinegar to the mixture, the indicator changed back because it reacted with the hydronium (part of the acid's compound). You could also try using toothpaste then orange juice with this indicator: this is why it tastes funny when you drink OJ then brush your teeth. The tooth paste is basic, and the OJ is acidic.