Dear Student, Natural indicator which we use in our daily lives are 1. Turmeric- If we place acidic substance in the turmeric paste no colour change will happen. If we put basic substance in the turmeric paste the colour change from yellow to red takes place. 2. Olfactory indicator which changes its smell when mixed with acid or a base. Paste of onion or juice when added with base loses its smell whereas no smell vanish out in acidic solution. Regards