Science, Tech, Math › Science What is a Universal Indicator in Chemistry? Definition, Composition, and Color Range for pH Share Flipboard Email Print GUSTOIMAGES/Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated September 22, 2019 A universal indicator is a blend of pH indicator solutions designed to identify the pH of a solution over a wide range of values. There are several different formulas for universal indicators, but most are based on a patented formula developed by Yamada in 1933. A common mixture includes thymol blue, methyl red, bromothymol blue, and phenolphthalein. How Colors Are Used Color change is used to identify pH values. The most common universal indicator colors are: Red 0 ≥ pH ≥ 3Yellow 3 ≥ pH ≥ 6Green pH = 7Blue 8 ≥ pH ≥ 11Purple 11 ≥ pH ≥ 14 However, the colors are specific to the formulation. A commercial preparation comes with a color chart that explains the expected colors and pH ranges. While a universal indicator solution may be used to test any sample, it works best on a clear solution because it's easier to see and interpret the color change.