We'd love to do a curses version of fish_config. I think you're right the default colors could be warmer and still work on light backgrounds (terminals don't publish their colors so the defaults have to work on light and dark).
Variables are still instantly propagated, it just uses fifos instead of a daemon!
Hi. There are actually some possibilities there, but it is not entirely reliable. Examples are xterm sequences and the COLORFGBG environment variable. Some terminals can be assumed to be dark such as the linux/bsd console or now vintage hardware.
Windows is most often dark, but there is an API to ask as well. However, I don't think fish works there. Perhaps from LSW.
Sounds like having default colors closer to medium gray is easier.
The web configuration bring in a hell lot of dependencies. Please make it a separate project.
Also if the readline part can be extracted to a separate executable, then it will be amazing. Imagine a fish like completion with psql.