Fix "color-red" that should be "error"

Author: frank-at-adacore

courses/ada_essentials/140_access_types/02-access_types.rst

@@ -23,7 +23,10 @@ Access Type
      type Rec_Access_2 is access Rec_T;
      Rec_Ptr_2 : Rec_Access_2 := Rec_Access_2 (Rec_Ptr);
 
-  :color-red:`example.adb:6:32: error: target type must be general access type`
+  .. code:: error
+    :font-size: footnotesize
+
+    example.adb:6:32: error: target type must be general access type
 
 .. note::
 

courses/ada_essentials/143_general_access_types/03-accessibility_checks.rst

@@ -39,9 +39,11 @@ Access Type Scoping Example
 
 .. container:: source_include 143_general_access_types/examples/accessibility_checks/nesting_example.adb :code:Ada :number-lines:1
 
-:color-red:`nesting_example.adb:12:23: error: non-local pointer cannot point to local object`
+.. code:: error
+  :font-size: scriptsize
 
-:color-red:`nesting_example.adb:17:39: error: cannot convert local pointer to non-local access type`
+  example.adb:12:23: error: non-local pointer cannot point to local object
+  example.adb:17:39: error: cannot convert local pointer to non-local access type
 
 * To avoid having to face these issues, avoid nested access types
 
@@ -62,7 +64,9 @@ Dynamic Accessibility Checks
 
 .. container:: source_include 143_general_access_types/examples/accessibility_checks/dynamic_accessibility.adb :code:Ada :number-lines:4 :start-after:snippet_begin :end-before:snippet_end
 
-:color-red:`raised PROGRAM_ERROR : dynamic_accessibility.adb:12 accessibility check failed`
+.. code:: error
+
+  raised PROGRAM_ERROR : dynamic_accessibility.adb:12 accessibility check failed
 
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 Getting Around Accessibility Checks