As in our previous 11-Plus Verbal Reasoning Same Meaning quizzes, all you need to do is pick the answer which expresses the closest meaning to the word in CAPITALS in the question.
Words can be tricky little things at times. Some words might be similar in meaning, but there are levels of 'strength' to be considered. As an example, take a look at the following two sentences.
Whilst angry and exasperated are synonyms, exasperated is a much stronger word than angry. Likewise with loud and deafening. The more you learn about English, the better you'll be able to express yourself with similar strength synonyms!
This would presumably involve clever selection of subtle colours, but there is no suggestion that the artist has actually confused (Answer 4) part of the ground-based landscape with something in the sky