Many natural substances contain molecules that change colour in aqueous solutions when the solution is changed from a basic to acidic nature or vice versa. Several natural dyes, e.g., the pigments in flowers or the coloured ingredient of turmeric have such properties. Quantitatively pH=-log[H+], is a measure of the acidity or basicity of a system. It varies from close to 0 (strongly acidic) to nearly 14(strongly basic).Common acid-base indicators when added in a small amount to a solution, give a visual indication of the pH of the solution. When an acid is neutralised by a base, some indicators show a sharp change in color near the point of neutralisation. These are also called halochromic compounds. In this experiment, we watch colours of solutions of different nature (acidic or basic) with indicators in a self learning mode.