posted by John .
Student A, you have a violet #4 diagram.
Student B, you have a colorless #4 diagram. Color the colorless # 4 diagram violet. [There is #4 in the triangle.] I mean color the # 4 triangle violet? Are you following me?
By talking to each other, you should color all the colorless diagrams colorful with a crayon or a ballpoint pen.
(Please check the passage of this activity as well.)
In the second sentence, I'd omit the words in brackets. The rest is fine.
In the third sentence, I'd omit the word "colorful." It's not needed.
Everything else sounds good.