Answer: Colombia
Step-by-step explanation:
The Spanish-speaking country that has a naturally occurring rainbow river is Colombia. The river is called "Caño Cristales," and it is located in the Serrania de la Macarena mountain range in the province of Meta. The river is known for its vibrant colors, which are caused by the unique mix of minerals, algae, and other natural factors in the water. The colors of the river change throughout the year, depending on the water level and other environmental factors, but it is most vibrant between June and December. The river has become a popular tourist destination in recent years, but efforts are being made to protect the fragile ecosystem and limit the impact of tourism.