Default REPL output is difficult to read on light background

[eschnett]

I'm using Julia on macOS, and my terminals have a light (almost white) background. The default color scheme of the REPL is difficult to read there, as e.g. yellow (for warnings) is almost unreadable.

This page has some hints for how to automatically detect whether the terminal background is light or dark.

[KristofferC]

For reference, the following env vars can be set to customize the colors, e.g.:

ENV["JULIA_ERROR_COLOR"] = :magenta
ENV["JULIA_WARN_COLOR"] = :yellow
ENV["JULIA_INFO_COLOR"] = :cyan

[eschnett]

Yes, I'm doing this. There are two problems: (1) It's not the default, and (2) this doesn't affect other parts of Julia, e.g. the package manager which still uses light grey for its status output.

I'm thinking that a function has_light_background in REPL's Terminals.jl (next to hascolor there) would make sense?

[ckoe-bccms]

Yes, having readable pkg status would be great. Eventually forcing everything to use just the terminals foreground color (effectively monochrome) might be the simplest temporary solution to do ?
Edit: forcing monochrome if requested by the user of course.

[KristofferC]

You could always start julia with --color=no.

[ckoe-bccms]

Ah, sorry for the noise then !

[vtjnash]

While the PR to autodetect doesn't seem like it will work well, so we haven't merged it in a couple years, I think the --color=light / --color=dark options presented there still have merit, if someone wanted to further develop those idea (there's still a couple days left in hacktoberfest)

[newptcai]

I change the default to

ENV["JULIA_WARN_COLOR"] = :cyan

But it does not seem to have any effect.

[adigitoleo]

Adding some suggestions to the discussion here, after I went through the same experience:

• Present the --color=no option more visibly in the docs (e.g. at https://docs.julialang.org/en/v1/stdlib/REPL/)
• The --color=light or --color=dark would help, IIRC IPython has something similar
• A way to list all REPL element names (similar to Base.text_colors but showing the element->color mapping) would be useful (maybe I missed it?) for figuring out what to put in the startup config.

[adigitoleo]

For reference, here's a quick snippet to get all the "named" colors:

julia> for key in keys(Base.text_colors)
           if isa(key, Symbol)
               println(key)
           end
       end

The names match the base 16 unix/X11/terminal/(?) color names, so you can use a command like (Linux):

msgcat --color=test|head -11

and compare the colors to see which ones you want to change. Preview changes by reassigning to the color dict, e.g.:

julia> Base.text_colors[:white] = Base.text_colors[:red]

When you're happy put the ENV declarations in the config file (see prev comments). So this kind of solves the last bullet point in my other comment.