As suggested here: #41423 (comment) it would be good to support theming Julia's colors. There's also #41295 but I think that may overcomplexify things. Without @staticfloat's input, I'm not entirely clear on how using Preferences in Julia would work, whereas I have a pretty clear idea about how adding a config file to theme Julia's colors would work: Instead of hardcoding colors, if Julia is run in color mode, it would look in a file called ~/.julia/config/colors.toml that maps uses of colors as keys to some kind of color description as values. Here are some questions:

1. What are the color keys? Presumably descriptions of how we use colors.
2. What are the color values? #123abc strings? ANSI color names? Either?
3. Do we need anything else in the file or is it just this map?

I think for usability we'd probably also want to have changes to this file take effect immediately, so we'd want to remember the inode, size, mtime and ctime and if any of them changes, reload the file. We also want to take care that if we're not using color the file never needs to be looked at.