address luke's comment

docs/concepts/events.md

@@ -120,6 +120,7 @@ graph TD;
     PlayerEvent-->CanPlayerSleepEvent;
 
     class Event,BlockEvent,EntityEvent,LivingEvent,PlayerEvent red;
+    class BlockDropsEvent,CanPlayerSleepEvent blue;
 ```
 
 ### Cancellable Events

docs/entities/livingentity.md

@@ -104,13 +104,16 @@ _See [Containers on Entities][containers]._
 
 ## Hierarchy
 
-Living entities have a complex class hierarchy. As mentioned before, there are three direct subclasses:
+Living entities have a complex class hierarchy. As mentioned before, there are three direct subclasses (red classes are `abstract`, blue classes are not):
 
 ```mermaid
 graph LR;
     LivingEntity-->ArmorStand;
     LivingEntity-->Mob;
     LivingEntity-->Player;
+    
+    class LivingEntity,Mob,Player red;
+    class ArmorStand blue;
 ```
 
 Of these, `ArmorStand` has no subclasses (and is also the only non-abstract class), so we will focus on the class hierarchy of `Mob` and `Player`.
@@ -181,6 +184,9 @@ graph LR;
     AbstractClientPlayer-->RemotePlayer;
     Player-->ServerPlayer;
     ServerPlayer-->FakePlayer;
+    
+    class Player,AbstractClientPlayer red;
+    class LocalPlayer,RemotePlayer,ServerPlayer,FakePlayer blue;
 ```
 
 - `AbstractClientPlayer`: This class is used as a base for the two client players, both used to represent players on the [logical client][logicalsides].

src/pages/contributing.md

@@ -297,6 +297,23 @@ I'm within an admonition!
 :::
 ```
 
+### Diagrams
+
+Diagrams can be created using the [Mermaid library][mermaid].
+
+When creating a diagram, a convention is used to make `abstract` classes red and non-`abstract` classes blue.
+
+````md
+<!-- Class1 is abstract, Class2 is not -->
+```mermaid
+graph LR;
+    Class1-->Class2;
+
+    class Class1 red;
+    class Class2 blue;
+```
+````
+
 [docs]: https://github.com/neoforged/Documentation
 
 [npm]: https://www.npmjs.com/
@@ -313,6 +330,7 @@ I'm within an admonition!
 [eck]: http://math.hws.edu/javanotes/
 
 [docusaurus]: https://docusaurus.io/docs/markdown-features
+[mermaid]: https://mermaid.js.org/intro/
 [mdx]: https://mdxjs.com/guides/
 
 [admonition]: https://docusaurus.io/docs/markdown-features/admonitions