What imparts the red colour to the bricks?

 At first, we need to understand the general chemical composition of a brick. A brick contains many chemical elements like silica, alumina, lime etc.

When we burns the brick, the iron content present in the soil gets converted into iron oxide which imparts in the red colour of a brick. 7% of iron oxide is sufficient to make the brick red.

If we burns the brick on low temperature, the iron content won't get converted into iron oxide completely. In this case, the bricks look pink in colour. Similarly, if the lime content increases, the brick will appear white.

Thus, the colour of  bricks depends on the chemical composition of the soil from which they are made.

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