Challenge 1: Shifting a Brand Color Across a 20-File Product — Solution Walkthrough

The answer:

Per this chapter's own material, the correct approach is to update the
color style's own underlying value inside the shared library file,
then publish a new version of that library. This pushes the update out
to every file using the library, updating every element that uses that
named color style throughout all 20 files at once.

Why editing each file individually would be the wrong approach:

Manually finding and updating the color in 20 separate files would be
slow and error-prone, with a real risk of missing an instance or
introducing a slightly different shade in one file by mistake — exactly
the kind of inconsistency this chapter's own material on style
propagation is meant to avoid.

Why this only works if the color was set up as a style in the first
place:

This propagation only applies to elements actually using the named
color style. Any element using a one-off, manually-entered color value
instead wouldn't update automatically — which is exactly why this
chapter's own warning box treats consistent style usage as something
that has to be actively maintained, not something guaranteed just by
the library existing.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that a company-wide color change is correctly
matched to updating a shared library's own color style and republishing
it, rather than manually editing every individual file.