Writer Roy Thomas, Vision’s co-creator, originally envisioned the character being all white, but due to printing limitations, he was instead made all red.
Vision later transitioned into his standard yellow, green and red color scheme, but in the West Coast Avengers book, the android’s reconstructed body was chalk-white, as seen below.
That being said, it wouldn’t have been unprecedented to have a gray/white-colored Vision.
You can head over to EW to see Ryan Meinerding’s concept art of Vision’s original look for Avengers: Age of Ultron, but had director Joss Whedon gone with this design, the Vision would have looked significantly different from the one currently flying around the MCU.