Red oxygen
Red oxygen, or tetraoxygen (O4) is an allotrope of oxygen occuring in extremely high pressures (in order of 20 GPa). Under such pressures the normally blue solid oxygen turns deep red, together with great reduction of its volume. Its absorption spectrum suggests the formation of O4 molecules. It is much more powerful oxidizer than oxygen or ozone, and its properties are being studied for use in rocket fuels and other applications, as it contains more oxygen in a smaller volume.
The existence of O4 molecules was predicted theoretically in 1920s, but only recently the mass spectroscopy experiments in Rome provided more existence. The shape of the molecule is still uncertain; presently it is believed that the mlolecule is composed of two dumbbell-shaped O2 molecules loosely bound together.
With further pressure increase, at 96 GPa oxygen becomes metallic.
Other meaning
Red Oxygen is a name of a company[1] providing SMS/email gatewaying solutions.