YOU SAID:

if turtles are green then carrots should be yellow

INTO JAPANESE

カメが緑色ならばニンジンは黄色でなければならない

BACK INTO ENGLISH

If the turtle is green, the carrot must be yellow

INTO JAPANESE

カメが緑の場合、ニンジンは黄色でなければなりません

BACK INTO ENGLISH

If the turtle is green, the carrot must be yellow