Explain default theme some more

src/e2ee/README.md

@@ -9,7 +9,7 @@ the prompt of the message bar:
 
 - Green <code style="color: green">[E]</code> indicates that the room is **encrypted**.
 - Red <code style="color: red">[U]</code> indicates that the room is **unencrypted**.
-- Yellow <code style="color: red">[?]</code> indicates that the room's encryption state is **unknown**.
+- Yellow <code style="color: yellow">[?]</code> indicates that the room's encryption state is **unknown**.
 
 Note that these are colored using the ANSI colors in the `default` theme, so depending
 on your terminal colors they may appear differently.

src/themes/gallery.md

@@ -4,6 +4,12 @@
 
 ### `default`
 
+This is the default theme, which uses only ANSI colors and doesn't change
+the background for any text, which means that it will look like how your
+terminal colors usually do. How this looks will depend a lot on your
+terminal's configuration, but it should work in many different environments,
+including those that don't support 24-bit True Color.
+
 ## True Color (24-bit)
 
 ### `apprentice-dark`