[Tom Edgerton]

Richard--

It's not a case of either/or, right/wrong....

You can gray a color back either by adding gray, or adding its complement.

To keep it simple, I think of it as follows:

If you add gray, it more gradually grays the color back. The value of the gray is a large factor in what happens here.
If you add its complement, it happens more quickly, and in a more complex--often richer--way.

From the above posts you can see that there are quite enough grays out there that you can play with.

Beyond this, I remind myself of what Friedrich Engels (1803-1882) said:

"An ounce of action is worth a ton of theory."

Best--Tom