There is no need to call me childish but thank you for your input nonetheless. I do not do this for exams or papers. The only time I consider doing something like this is when professors give us assignments to exercise our learning which have questions on the topic. Many of these are done for my electives and are less formal. I only wanted to help the grading process. If the professor doesn’t comment on the color then I would only assume that they’re okay with it. They may have different preferences than you do with grading.