PxSe1-x glasses cover almost entire composition range from pure Se to P0.84Se0.16. In addition, red phosphorus is usually also amorphous. The P4Se3 cage compound, situated in the gap between the two glass-forming regions cannot be obtained as a glass at normal conditions of synthesis from the melt. Nevertheless, we have synthesised the P4Se3 glasses at high pressure and temperature. Depending on synthesis conditions, glasses of different colour: from dark yellow to red, brown and finally black can be obtained. All these polyamorphic glasses seem to have a mixed molecular/network structure. The suggested neutron diffraction measurements at ISIS will allow the precise direct structural information to be obtained. The neutron diffraction results will be combined with our high-energy x-ray diffraction measurements, Raman and 31P NMR experiments as well as with EPSR and RMC modelling.