Intus uses a high-tech proprietary German engineered laminate that is infused into the PVC at the factory. Not only does the "u" PVC have UV inhibitors in the PVC itself but they can install the
RENOLIT EXOFOL FX over the uPVC at the factory
which consists of 3 layers. The top layer consists of a polyvinylidene
fluoride film, the
second is transparent polymethylmethacrylate (PMMA) and the base layer
is a solid colour PMMA. The base layer contains Solar Shield Technology
(SST), to further
decrease heat build-up of the film and the laminated components,
including radiation damage.
The three-layered structure of the film retains any color nearly
without change throughout the service life, even when subjected to
intense UV exposure.
In high-elevation or intense UV areas, I would still recommend staying with a lighter color. Darker colors will tend to absorb more heat. The same applies for wall color and roof colors. Lighter colors tend to not get as hot as darker colors.
Here is the link to the German company that makes it:
RENOLIT EXOFOL