An Indicator.
Curcuma (turmeric) is red in an alkaline solution and yellow in an acidic solution.
Depending on the pH solutions have different colors with a pH paper.
Chlorophyll is the substance that gives plants their green colour.
Earth is the substance of the land surface, where we have a variety types of soil with different colors.
blue
Black colour
The colour is red in acidic solutions.
a long, thin line or mark of a different substance or colour from its surroundings. or, an element of a specified kind in someone's character.
in neutral solutions ph paper turns to blue!
aluminum sulphate is colourless
not quite sure...
Chlorophyll