On May 1, 1840 Britain issued the first adhesive postage stamp. The ticket was called Penny Black and had on it the picture of Queen Victoria. (See picture on the right.) All in all the British postal department had issued 6,81,58,080 Penny Blacks, but after that its printing had to be discontinued.
It so happened that the ticket having value of a penny was black in color, just as its name suggests. And the ink of the stamp that the postal department put on tickets to cancel the used tickets was black too. Thus it was nearly impossible to differentiate between used and unused tickets, and many people started reusing them. As a result, only in the second year of the issue of Penny Black the postal department had to turn to printing, instead of Penny Black, a red inked stamp called Penny Red.
Penny Black (Wikipedia)
Penny Red (Wikipedia)