As an AI language model, I do not have access to the specific context in which the researcher made this statement, but in general, the researcher might believe that if CO2 had a visible color, its harmful effects would have been more easily observable and therefore addressed more urgently. CO2 is a greenhouse gas that contributes to global warming and climate change, but its effects are not immediately visible to the naked eye. If it had a color that made it more noticeable, it might have been taken more seriously as a threat to the environment and human health.
