Reference request for research on images or colors used in quizzes and exams
With a quick Google search, I found the following, but I am interested if there is anything more than these, especially with mathematics or studies with images:

"Effect of Paper Color on Students' Physics Exam Performances" by David R. Schmidt, Todd G. Ruskell, and Patrick B. Kohl

https://www.academia.edu/5702205/Effect_of_Paper_Color_on_Students_Physics_Exam_Performances 

"The Non-Impact of Paper Color on Exam Performance" by Michael J. Meyer and Jennifer Bagwell:
http://aaajournals.org/doi/abs/10.2308/iace-50142

"Effect of Paper Color and Question Orderon Exam Performance" by Ilanit R. Tal, Katherine G. Akers, and Gordon K. Hodge

https://www.researchgate.net/publication/233180281_Effect_of_Paper_Color_and_Question_Order_on_Exam_Performance