Edit: this pic i posted isn't actually "testing phase paint", this one is. Still badass, tho
They use camouflage paint/wrap to hide the styling and body lines until they’re ready to officially release the vehicle.
Its Dazzle Camouflage and dates back to around WW1 as a way of hiding identifying features of a ship.
The geometric patterns and sharp color transitions make it difficult to pick out curves and contours on the car which is good for keeping updated body styling hidden. Generally manufacturers will need to build a couple units of a new model to test out on the road or tracks to confirm handling of performance, but they don't want people seeing the new body curves or the "freshness" of it all will be spoiled before they can show it off at a big autoshow.
While the answers in regards to the Dazzle camo are on point, I think your example is just a custom wrap job.
This is actual Dazzle camo.
The type of camuflage used is called dazzle camuflage. The concept is that the contrasts and stripes make it very hard for people to see the lines in the design. So it is very hard to copy the design from just a few pictures. There is no way of knowing if a darker area is due to the paint scheme or if it a shaddow cast by the body design. In your image you might notice that it is very hard to see how the lines around the fenders joins up with the side panels of the cars. There is also a feature on the engine cover in front of the gills which might be an air inlet to the engine bay but you can not really see how it is shaped.
While dazzle paint has its history in "hiding the lines" of a car (which it's not so great at if you've ever seen one in person), these days it's also intended to stop photogrammetry tools from being able to produce an accurate 3D model of the car before it's released, and the designs have been tweaked for that very purpose.