Answer:
i believe it is 18
Explanation:
green1 green2 blue red1 red2 red3
green2 green1 blue red1 red2 red3
green1 green2 blue red2 red1 red3
green2 green1 blue red2 red1 red3
green1 green2 blue red3 red2 red1
green2 green1 blue red3 red2 red1
green1 green2 blue red1 red3 red2
green2 green1 blue red1 red3 red2
red1 red2 red3 blue green1 green 2 everthing above but this way