This isn't that usual question . We have learnt to answer in our primary schools days , with a lot of childish pride .
It's more than that . It goes far to the early Islam civilization and was
associated with a horrible pandemic the spread among big Islamic cities at that time .
The face of a sick person had 3 colors red , yellow and blue . As long as his face is red or yellow , there is hope for him to survive but if his face has the blue color , that's mean he is going to die .
The 17 hejrah c