I asked because I figured you'd give a different definition than the one I'm familiar with.

Black Hat -> Using vulnerabilities to break into other people's computers.

Gray Hat -> Using information gleaned from breakins to other people's computers to find new vulnerabilities.

or

Gray Hat -> Finding vulnerabilities and supplying them to people who break into other people's computers while retaining deniability about the actual breakins; ie, supplying your friends without wanting to know what they're doing with the exploits.

The 1990s "gray hat" would be the guy using leaked SunOS 4.1.3 source to find vulnerabilities.

Your distinction isn't invalid; these "hat colors" have always been confusing.