Top brown surface =

= 3.142 x 16 x 16 = 804.352 square inches
Side Brown surface =

= 2 x 3.142 x 16 x 6 = 603.264 square inches
Side Green surface =

= 2 x 3.142 x 16 x 8 = 804.352 square
Total Surface area = 804.352 + 804.352 + 603.264 = 2211.968 square inches
% that is green = 804.352 ÷ 2211.968 x 100% = 36.37%