The author's purpose who is Adam Alter is to attempt to get teachers to stop using red pens to grade their students work. I believe he wants this is because the color red shows that the students have been assessed harshly when their work is covered in red ink. To me this isn't really important as it most likely only affects people in elementary school as they are more likely to express their feelings then people in secondary school. When speaking to my siblings on the topic to them the color red when grading work influences the mind that they made to many errors which resulted in their bad performances, as this may not make the most sense if you think about it in some religions the color red represents death and evil.
-- Sorry if this isnt a lot I attempted to finish this as best and fast as I could