If you see red, you become very angry about something.
The teacher will see red when he finds out you haven't done your homework again! He'll give you detention.
My mum saw red when I came in late for dinner.
I saw red and shouted when the boss complained about my work for the third time today.
Don't confuse it with
If you lose your temper easily, you can say you fly off the handle.
When Simon told me he was going out for the third night in a row, I really flew off the handle and shouted at him.
The colour red is associated with many different emotions, including anger and danger, probably because it is the colour of blood. Many road signs use the colour red to warn motorists of hazards. Red also has strong links to love and passion, and, in many cultures, symbolizes happiness and celebration.