The students have line drawings and the teacher gives them intructions on how to color the drawing. The instructions are not direct commands, instead, the teacher "dictates" sentences and the student must listen and understand how the picture is to be colored.
For younger children the "dictation" can be very simple: "three blue balls", "a yellow car", "the green tree".
With older children a teacher can use full sentences: "The boy on the left is wearing a red hat." or "The girl under the tree has blue shoes."
Repeat each phrase or sentence several times before moving on. Give the children plenty of time for coloring. They also need time to reflect and to transfer what they are hearing into what they are doing.
The students will probably "copy" each other. This is fine, language transfer will still occur because there is still an association with what they heard and what they are coloring.
Don't be afraid to continually add more complex sentences as they get used to this type of "dictation". Children love the challenge and they will listen carefully to avoid making costly mistakes (it's very difficult to erase coloring pencils).