When our seniors told us that the blue end of the eraser could help us correct our mistakes we made with our pens, it blew our naive little minds. We tried it and we all failed, miserably. That is a lie that has its place right next to 'Santa Claus is real' and 'the popular game - Ice Pice - is actually I Spy'.
We were confused about this whole issue but we finally found a conclusive answer to the question -
The blue end is meant for erasing pencil marks on heavy grades of paper or dark marks.
The soft end (pink/orange) is useful for light grades of paper which the hard gritted side would tear apart, and also for precision erasing, such as removing a light stray mark from among dark marks.
On grainy art paper, pencil marks are a pain to remove. The blue end of the eraser is tough and it doesn't wither away on being used on a more coarse form of paper.
We had always believed that the red part was to erase the writing, and the blue part was to erase the paper. But after this revelation, we thought that we had finally solved the mystery that had plagued our otherwise innocent childhood. And then we came across something that messed with our brains.