Traffic lights are not only about red, amber and green. In theory questions, you also need to read the whole situation.
Look for lane arrows
An arrow can change which direction is allowed. Always check whether the signal applies to your lane.
Watch for vulnerable road users
Pedestrians, cyclists and public transport may have separate signals. The safest answer usually depends on noticing them.
Combine signals with signs
Road signs and markings can add detail to the signal. Read them together before choosing your answer.

