How do we see colour?

My teacher told that electrons in compounds absorb certain characteristic wavelength of white light and we absorb the colour complementary to the colour that it absorbs. But anything in excited state has to return to ground state and this is accomplished by emitting the colour of light absorbed. Today we had... show more My teacher told that electrons in compounds absorb certain characteristic wavelength of white light and we absorb the colour complementary to the colour that it absorbs.

But anything in excited state has to return to ground state and this is accomplished by emitting the colour of light absorbed.

Today we had flame photometry class and I got this doubt when I saw that calcium gave brick red colour when kept in flame and only red. I could never see the complementary colour to red anywhere .....
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