[mayd85]

I remember, the initial mules of Tata Nexon were tested with Tata Zest body shells since they have the same underlying platform. It used to appear very weird, a Zest with oversized wheels.

[A.K]

Deviating from the camo topic a wee bit to something I found particularly interesting. Manufacturers often test the engine and running gear of the cars on different bodies (cue GaryTSI's post).
Jaguar very famously tested the XJ220 engine on an inconspicuous Ford Transit van! Very fascinating, more so since the XJ220 was the fastest production car on the market when launched. It was later pipped by the McLaren F1 whose BMW V12 motor too was tested on an E34 BMW M5 Touring body.
Both these cars survive, the Ford Transit van was later acquired and restored by Jag specialist Don Law Racing and the V12 powered M5 remains stashed away with BMW.
Interestingly, when Mercedes-Benz built the CLK GTR, they bought a used McLaren F1 GTR (Chassis 011R) to serve as a mule for the CLK GTR. Mercedes built the CLK GTR in record time and once the car was finalized for production, 011R was reverted to its original form and listed for sale.

[Rehaan]

This "low-res" camo on the Hyundai Vision FK is pretty cool:

[ads11]

I remember about May 2012 somewhere Sorbas in southern Spain (iirc nearest big city was Almeria), we were doing fieldwork along this winding stretch of road that snaked up and down this small hill. As we worked our way up this road looking at the outcrops, there was a 991 series Porsche 911 test mule going up and down this stretch of road all day. The driver stopped at one point and had a brief chat and we remember looking inside and the interiors were a maze of wiring and screens, with all sorts of boxy telemetry equipment where the passenger seat would be, with one of those Panasonic Toughbook laptops mounted in reach of the driver. While the car didn't have any dazzle camo as such it was totally blacked out and had a very rough unfinished vibe to it. I guess the driver was doing final testing because the car launched later that year I believe. We weren't allowed to take photos, and besides we had rubbish cameras but I guess the driver was amused because this was an otherwise empty area except for the handful of undergrad geologists in their hi-viz jackets pottering about the hillside. I do remember he didn't hold back at all, gunning it up and down the hill, with the sound properly echoing off the valley floor.

That's my main memory of coming close to a very discrete, somewhat camouflaged test vehicle.

[BlackLight]

I've seen several Skodas do a high speed runs on Mumbai Pune express way. They just go full throttle without bothering about speed cameras. It must feel amazing and invincible as a test mule driver.