Light is an important communication modality. Smart speakers leverage light behaviors with different colors and shapes to deliver a wide range of information. However, there has not been sufficient work to assess the effectiveness of these light behaviors. That is, can users correctly interpret light behaviors from smart speakers? How effective are these light behaviors across different cultures? To answer these questions, we conducted a survey with 1,006 smart speaker users from seven countries. On average, they were able to correctly identify only 37% of light behaviors used in smart speakers. Overall, Amazon Echo users accurately identified a higher proportion of light behaviors than Google Home users. Furthermore, the perceived usability varied considerably across different countries. We also interviewed six experts to design more effective light behaviors for smart speakers. Our findings have important implications for future smart speaker design and the use of light as a communication modality in HCI.