What have studies shown about different dark background colours

I am looking to redesign a website over which I have little control outside the colour scheme. I want to find usability evidence to back up my change decisions, or else use that evidence to adjust my proposal.

The current website has a dark blue background behind the text area (#1b3676 background with #D5D4D4 text). Because of the overwhelming blueness throughout that design, I want to change to a design which instead has a more bluey-charcoal colour behind the text area (#2d3c53 background with the same #D5D4D4 text). There are to be other colour changes around the place, such as the use of an accent colour which looks better on the darker background, but the legibility of these two colour schemes is what's in question here.

Snippet comparing the old to the proposed new:

I've been trying to search for articles on Google which compare the legibility of light text on differently coloured dark backgrounds, but whatever I try, "dark background" is always interpreted as meaning "black background everywhere" rather than "background colour that is darker than the text colour in the reading pane". Because of this, I can't find anything to confirm or rebut my suspicion that it's easier to read the text on the less coloured background than the more coloured one, despite the fact that there is slightly higher contrast with the bluer blue.

Are there any good studies or articles comparing usability of different coloured dark backgrounds?

Edit: Links to the example pages (colours relevant only): Existing / Proposed