When I was in school (a few years after I graduated), we had one jamshut instead of a cleaner. So, one day, some idiot wrote on the wall "X*Y" in black. Jamsut was instructed to paint this unnecessity, since the wall was yellow, he mixed the yellow paint and painted it right above the black. The inscription remained, but instead of black color acquired dark orange. The director glanced and ordered to paint the whole wall with a different paint, now we have a green wall in the yellow corridor with again standing out, this time because of the number of layers of paint, clearly so the bugs pass, close to disassemble the eye is easy. The director was angry and said to cut off this "x*it". The next day we had a green wall in the yellow corridor with a brick-shaped inscription "X*Y".