Added ToString and DebuggerDisplay

Casting a hex :ok-hand:

src/Discord.Net/Entities/Roles/Color.cs

@@ -32,6 +32,11 @@
                 ((uint)(r * 255.0f) << 16) |
                 ((uint)(g * 255.0f) << 8) |
                 (uint)(b * 255.0f);
-        }        
+        }
+        
+        public override string ToString() =>
+            $"#{Convert.ToString(RawValue, 16)}";
+        private string DebuggerDisplay() =>
+            $"#{Convert.ToString(RawValue, 16)} ({RawValue})";
     }
 }