"Let chemistry go to the public" is the slogan of National Chemistry Week. The theme of American Chemistry Week involves all aspects of chemistry, but it is closely related to the daily life of the public. A, we live in the material world, not only there are all kinds of substances, but also substances are constantly changing, and chemistry is the science of studying substances and their changing laws. The colorful world is related to chemistry, so that's right.

B, food chemistry mainly studies the processing and storage process of food, including many chemical changes and principles, which are related to chemistry, so it is correct.

C. Hydroelectric power generation is to convert the potential energy of water into electric energy, which is a field of physical research and has nothing to do with chemistry, so it is wrong.

D. chemistry is a natural science that studies the composition, structure, properties and changing laws of substances. The composition of the earth and the distant atmosphere is one of the research contents of chemistry, so it is correct.

So choose C.