White and Not so white

It was one of those days this week when I had no quiz in the morning.One of my Profs whose exam we had just the day before, had already corrected the papers and distributed them in the class.Then,he started writing the correct answers on the board under two headings - white and not so white,as I rummaged through the pages of my answer script searching for a source of getting extra marks.White and Not so white?!?I looked around and found that my friends were equally startled.We didn't have the oppurtunity of looking at the questions after the quiz as it was a question cum answer paper.So,now as we looked at each other's paper,with a little difficulty we could make out that if the colour of of one paper was R-255 G-255 B -255,the other's was R-255 G-251 B-252.And,indeed the options of multiple choice questions were jumbled,values of numericals changed( marginally,though) keeping the overall format the same.Smart way to prevent cheating!!!Now,this makes me wonder- What's next???
As i kept wondering,these ideas came into my mind
* Black and Dark Grey (colour of ink)
* Regular and Bold
* Normal and Abnormal (Font size)