Thin film interference
Rays reflect inside a thin film of plastic. The two (or more) emerging rays have travelled different path lengths and their wave crests might be in-phase or out of phase or in some in between condition.
The in-phase condition depends (like birefringence) on viewing angle and colour.
We see patches of colour but in general they are weaker than those from birefringence.
Soap film colours are from thin film interference.
Laminated toughened glass is anisotropic and this causes it to be birefringent. Light entering it splits into two distinct rays which are polarised and refracted differently.
The two rays have slightly different optical path lengths as they traverse the glass. On emerging, their wave crests can be in phase and combine to give a bright colour. They could also be out of phase giving less or no light. The phase condition depends on the wavelength (colour) and the viewing angle. We see coloured patches!
The colours are irregular because the anisotropy is generated as the glass is heated and cooled to laminate and toughen it. The mirror symmetry of the colours on the two windshields speaks volumes that they are the result of anisotropy and strains deliberately introduced during manufacture.
Birefringence is best seen by illuminating the material with plane polarized light and then viewing or photographing it through a second polariser. The colours can often be seen without deliberate polarization. The multi-layered windows act in themselves as partial polarisers.
Passenger windows are also birefringent and can generate bands of false colour especially on photographs.
Car windscreens have toughened laminated glass – they show similar (but weaker) colour patterns.