Final answer:
In the bromine test, the presence of an alkene is indicated by a color change from red to orange.
Step-by-step explanation:
In the bromine test, the presence of an alkene is indicated by a color change from red to orange. Bromine is a brownish-orange color, but when it reacts with an alkene, the orange color disappears. This happens because the alkene reacts with the bromine, causing the color change.