Yes—pink, purple, and red tones can occur naturally at sunset. The main cause is atmospheric scattering: when the sun is low, its light travels through more atmosphere, and shorter wavelengths are scattered away differently than when the sun is high, leaving warmer colors more visible.

That said, a photo can also be made more dramatic with filters or editing. In the example discussed, one clue was a bluish cast on the ground, which suggests the photographer may have used graduated color filters. The photographer was also noted to use Lee filters in other images, so the colors in that gallery may be enhanced rather than purely natural.

So the short answer is: such colors can be real, but strong pink/purple skies in a photo may also be boosted by filters or post-processing.