1. Out of the blue 意想不到地
I had nearly given up hope when out of the blue I was nominated by the university as a student ambassador.
2. Once in a blue moon 千載難逢地
Kelvin always fails his English tests. However, he scored 80 marks in the previous exam once in a blue moon.
3. Talk a blue streak 滔滔不絕
Jessica got home after a long vacation in Canada. She talks a blue streak to her family about her travel experiences even though it is already around midnight.
4. Give the green light 准許
The employees were given the green light to start working on the new real estate project.
5. Green around the gills 臉色蒼白
Jessica suddenly looked green around the gills after lunch, so she got off work three hours earlier than usual.