Challenge 1: Changing the Master Slide's Title Colour — Solution Walkthrough

Steps:
  1. View > Master Slide.
  2. Select the title placeholder on the master itself and change its
     font colour.
  3. View > Normal (or click "Close Master View").

Which slides updated:

Every slide in the presentation currently using that specific Master
Slide updates to the new title colour — regardless of which Layout
each individual slide happens to be using.

Why this matches Word & PowerPoint Chapter 8's own exercise:

The underlying mechanism is identical: a shared design definition
(the Master Slide here, the Slide Master there) sits above every
slide built from it, and editing that ONE shared definition updates
every slide reading from it simultaneously — exactly the "define
once, apply everywhere" behaviour Word & PowerPoint Chapter 8
demonstrated with PowerPoint's own Slide Master. The only difference
is the panel it's reached through (View > Master Slide here vs. View
> Slide Master in PowerPoint); the propagation behaviour itself is
unchanged.

WHY THIS WORKS AS AN ANSWER
------------------------------
This is a direct, hands-on confirmation of this chapter's own opening
claim: despite Impress organizing Master Slides and Layouts somewhat
differently than PowerPoint, the actual "edit the shared definition,
watch every dependent slide update" behaviour transfers completely
unchanged.