Dark-mode: A/B test green vs blue vs white #40

At present, dark-mode defaults to a simple reversal: black-on-white turns into white-on-black*. But this has some visual downsides - it is hard to get the brightness right, and there is some inherent moire or ghosting to such harsh contrast.

There are 3 other viable colors which could be the 'negation of black' for dark-mode. Red, and green or blue:

'Red' is ideal in some ways (see rubrication) and in theory should less damage sleep/melatonin (hence its usual use in low-level lighting), but it is unfortunately skunked by the association with horror, vampires, goth teens, FPSes etc. So that leaves blue and green.

In a 2019-11-26 poll on Twitter of my followers about preferred color for Dark mode, the results were (n = 177):

1. blue: 43%
2. green: 29%
3. neither: 28% [tacit endorsement of 'white'? no idea what other color they could seriously be preferring]

This is highly balanced, unfortunately, and it's not viable to make it configurable (since most users are first-time readers and even returning users rarely configure anything), and we have to pick one - even if just to declare firmly that it will always be 'white'.

So this seems like a good thing to run an A/B test on.

We can use the usual per-day setup and randomize triplets of white/blue/green for dark-mode users and look for overall traffic effects in Google Analytics, and put in a JS stub to override the default white CSS.

* Examples: https://gwern.net/doc/meta/2025-08-08-gwern-gwernnet-desktopheader-blogversion-darkmode.png https://gwern.net/doc/cs/css/2023-11-19-gwern-gwernnet-linkunderlining-darkmode.png https://gwern.net/doc/cs/css/2023-08-21-gwern-gwernnet-mobile-darkmode-aunnpagetop.png https://gwern.net/doc/cs/css/2023-08-21-gwern-gwernnet-desktop-index-darkmode-pagetopwithtoggleopen.png https://gwern.net/doc/cs/css/2021-03-28-gwern-gwernnet-annotations-mobilepopins-darkmode.png