Better Proof Highlighting

[mechtaev]

When Modus is used in Gnome Terminal with the default light theme, image literals are highlighted using a too bright color. It might be better to use the color of directories to highlight image predicates, because they are guaranteed to have good constrast in any color theme:

[mechtaev]

We can also consider highlighting only the names, but not the arguments

[thevirtuoso1973]

I just remembered there is this feature https://docs.rs/colored/latest/colored/trait.Colorize.html#method.on_black which will ensure it is always readable (by setting a section's background color to black regardless of the user's terminal color). But may not look that nice.