Yamada Universal Indicator

To prepare 1000 mL indicator, dissolve the following amounts in 500 mL ethanol:

0.025 g Thymol Blue
0.060 g Methyl Red
0.300 g Bromothymol Blue
0.500 g Phenolphthalein

Neutralize the solution (to green) with 0.05 M NaOH and dilute to 1000 mL with water.

The colors one gets are

pH 10: violet
pH 9: indigo
pH 8: blue
pH 7: green
pH 6: yellow
pH 5: orange
pH 4: red

Reference: Foster, Laurence S. and Irving J. Gruntfest, "Demonstration Experiments Using Universal Indicators", J. Chem. Ed., 14, 274 (1937)