Red diamonds?

BTW did anyone say what caused the redness? 

The source of color is imperfection in crystal lattice of the
diamond. In order to show any color (nitrogen containing diamonds
are excluded from this discussion), crystal lattice has to absorb
some part of the spectrum. The reason for rarity of red is because
crystal lattice has to absorb all the spectrum except red, and that
is truly rare.

Leonid Surpin