As of now, there are several greys are very similar, used across multiple areas of pgAdmin with no overlaps on color.
Here are the greys organized by scale, with the narrowed down greys underneath:
The palette of 6 greys is flexible enough to be used across all the areas within pgAdmin, and easier to map consistency.
Here's what it looks like with the 6 greys
Dropdown menus
Change from having white hover to dark grey, keeps text color the same
Query tool
I think some interesting things with color contrast are introduced once we look at the uneditable query editor as accessed through 'View all Data'.
We can address this either by changing the greys in the results table, or changing the grey in the query editor. As of now, I think changing the query editor grey might work better to make sure that when columns are selected in the 'Data Output' panel, they stand out with the blue.
If we lighten the editor table and fade out the text in the editor, it would look like this: