pH stands for the power of hydrogen. pH that ranges form 1-6.9 are acid substances. At pH 1 - 2.9, the substance is highly acidic which will have the color from red to red - orange. At pH 3 - 4, the substance is mildly acidic and the color range is from red - orange to orange. At pH 4.1 – 6.9, the substance is weakly acidic and the color range is from orange to yellow. At pH 7, it is neutral and it is green in color. At pH 7.1-14, it is basic. At pH 7.1 - 10.9, the substance is weakly basic the color range is from green to blue. At pH 11 - 13, the substance is mildly basic and the color range is from blue to purple. At pH 13.1 – 14, the substance is highly basic and the color range is from purple to light purple.
