What gives rise to the color of sapphires?
The blue of sapphires is produced by the elements titanium and iron that are both present. There is a process called charge transfer causing the transfer of an electron between Ti$^{4+}$ and Fe$^{2+}$ to Ti$^{3+}$ and Fe$^{3+}$ to fit together with the Al$^{3+}$ of the corundum lattice. Those ions give the blue sapphire its colour.

Note that the ions in a crystal are different from isolated ions in the gas phase, they tend to have larger absorption bands instead of sharp lines. Also the distances in the lattice are important and may modify the colour, anisotropy can lead to colour dichroism, the sapphire may be blue viewed from one side and green from another.