Cambridge Secondary (7-9). Stage 9. Science. Learner's Book - Unit 2: Properties of materials - Question 34

Group 7 data: fluorine (F): atomic number 9, electronic structure 2,7, mass number 19, pale yellow, melting point −220 °C, boiling point −188 °C; chlorine (Cl): 17, 2,8,7, 35, yellowish green, −101 °C, −34 °C; bromine (Br): 35, electronic structure missing, 80, brown, −7 °C, 59 °C.

What is the trend in colour in Group 7?