Litmus indicator solution turns red in acidic solutions and blue in alkaline solutions - and it turns purple in neutral solutions. Litmus paper is usually more reliable, and comes as red litmus paper and blue litmus paper. The table shows the colour changes it can make.
In this regard, what Colour does blue litmus paper turn in base?
Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple.
Why do you need to use both red and blue litmus paper to determine pH?
Indicators are organic substances that change colours at certain pH values. In order to determine whether a substance is an acid or base you must use both red and blue litmus paper. This is mainly to determine if the substance is neutral because the paper will stay the same colour in both.
What is an indicator for acids and bases?
Acid - Base indicators (also known as pH indicators) are substances which change colour with pH. They are usually weak acids or bases, which when dissolved in water dissociate slightly and form ions. Consider an indicator which is a weak acid, with the formula HIn.