According to this old Dartmouth Syllabus from 1994
http://www.dartmouth.edu/~chance/course/Syllabi/UCSD/section3_20.html
M&M Mars consumer affairs states that the color ratio for the candy is
30% brown
20% yellow
20% red
10% orange
10% green
10% tan
Clearly things of changed. Tan is no longer available, and Blue has been added. And now today, I just opened a bag that was easily 50% green.
Are there any more recent stats on M&M color ratio?