Hexane is a colorless liquid
Bromine is a corrosive and poisonous brown liquid
Exposed to light, the mixture of these two liquids loses its color.
Bromine reacted with hexane to form a colorless product.
Blue litmus paper reddened under the influence of hydrogen bromide.
Thus, the bromine reacted with hexane to form a colorless product, bromohexane, and hydrobromic acid:
$ C_6H_{12}+Br_2 \; \rightarrow \; C_6H_{11}Br + HBr $
An $H$ atom from hexane was replaced with a bromine atom: This is a substitution reaction.
