In a certain change, the color of a substance changed. What reaction might this be? 

The elements that interact in a reaction are known as reactants, and the substance that results from the reaction is known as the product. Catalysts are the other chemical substances that are utilized to quicken the reaction procedure. Changes in response typically fall into one of two categories: chemical or physical. The makeup of these two responses differs. A physical response alters the sample's appearance, smell, and display without altering the sample's composition, whereas a chemical reaction affects the composition of the components. Physical modifications include variations in color, warmth, texture, shape, and condition. Different chemical changes take place. When a substance's composition changes, this chemical change happens. Usually, it happens when old bonds dissolve and new ones form. - Temperature, color, odor, or the production of precipitate or bubbles are all signs of a chemical shift.
Therefore, based on the possibilities provided, we can conclude that the color of the components changed during chemical synthesis or reaction.

A change in color may be accompanied by a chemical change. A change in temperature, color, and formation of gas and precipitate is indicators of a chemical reaction. Thus chemical combination is the correct answer.

Hence, option B is correct.