Litmus paper changes color based on the acidity or alkalinity of the tested substances, turning red in acids and blue in bases.
Red litmus paper will turn blue when placed in a base (alkaline solution). Conversely, blue litmus paper will turn red when placed in an acidic solution. In the case of testing substances like vinegar (acid), soap (base), laundry detergent solution, and a saltwater solution, the litmus paper color changes will indicate the nature of the substances.
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