Color flash effect fixes (#18952)

Content.Shared/Effects/ColorFlashEffectEvent.cs

@@ -20,4 +20,4 @@ public sealed class ColorFlashEffectEvent : EntityEventArgs
         Color = color;
         Entities = entities;
     }
-}
+}

Content.Shared/Effects/SharedColorFlashEffectSystem.cs

@@ -0,0 +1,8 @@
+using Robust.Shared.Player;
+
+namespace Content.Shared.Effects;
+
+public abstract class SharedColorFlashEffectSystem : EntitySystem
+{
+    public abstract void RaiseEffect(Color color, List<EntityUid> entities, Filter filter);
+}