Yup, that's the utilitarian reason for having a different design for each week. Most companies didn't go so far however. But even the monthly passes that I used

Yup, that's the utilitarian reason for having a different design for each week. Most companies didn't go so far however. But even the monthly passes that I used in Romania during my youth were printed with different background colors every month (http://1.stpt.ro/forum/index.php?s=9978f358f69f69336b0cefcc552e709f&app=core&module=attach&section=attach&attach_rel_module=post&attach_id=175990 http://1.stpt.ro/forum/index.php?s=9978f358f69f69336b0cefcc5...).