That's true and as I said, I talked to the owner of the shop and he's been a marine mechanic since the late 60's. He assured me that this is the correct color for a Volvo 270 outdrive.
I asked him the same question since when I bought my XK, the drive had been repainted white. His answer was that over the years, the blue gray had more than likely faded the blue color out of it and looked white. Or when it faded, someone thought it was white and repainted it white.
He is also a certified Volvo Mechanic and claimed that he owned an XK22 at one point too. So I tend to believe him on the color. Short of seeing an all original boat for the early 70's that hasn't had the outdrive repainted, it's hard for the to argue with him over the color.
But 20 odd years ago, I personally stripped a 1973 Renell 23' boat that had a fire inside of it. One of the parts I salvaged was a Volvo 270 drive. It's in my pile of spare parts and it is a blue gray color.