[mediaqueries-5] Add note about how printing preferences aren't necessarily the same as screen preferences and maybe you want to consider the constraints of physical ink on paper. #3522

Author: fantasai

mediaqueries-5/Overview.bs

@@ -631,6 +631,16 @@ Detecting the desire for light or dark color schemes: the 'prefers-color-scheme'
 
 	</dl>
 
+	Note: User preferences can vary by medium;
+	for example, a user may prefer dark themes on a glowing screen,
+	but light themes when printing
+	(to save ink
+	and/or because inked text on blank paper prints better
+	than blank letterforms knocked out of an inked background).
+	UAs are expected to take such variances into consideration
+	so that 'prefers-color-scheme' reflects preferences appropriate to the medium
+	rather than preferences take out of context.
+
 	Issue: Should we include 'forced-light' and 'forced-dark' values? We don't necessarily want the
 	page to try to undo what the system might be enforcing.