Add proto message for MaterialColor. (#414)

* Add proto message for MaterialColor.

This proto message allows for changing the material colors of
an entities visual.

Signed-off-by: Benjamin Perseghetti <bperseghetti@rudislabs.com>

proto/gz/msgs/material_color.proto

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2024 CogniPilot Foundation
+ * Copyright (C) 2024 Rudis Laboratories LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+*/
+
+syntax = "proto3";
+package gz.msgs;
+option java_package = "com.gz.msgs";
+option java_outer_classname = "MaterialProtos";
+
+/// \ingroup gz.msgs
+/// \interface MaterialColor
+/// \brief Color description for an entities link-visual material.
+
+import "gz/msgs/color.proto";
+import "gz/msgs/header.proto";
+
+message MaterialColor
+{
+  /// \brief Optional header data
+  Header header          = 1;
+
+  /// \brief Name of link-visual.
+  string name            = 2;
+
+  /// \brief Name of parent enitity for link-visual.
+  string parent_name     = 3;
+
+  /// \brief Ambient color
+  Color ambient          = 4;
+
+  /// \brief Diffuse color
+  Color diffuse          = 5;
+
+  /// \brief Specular color
+  Color specular         = 6;
+
+  /// \brief Emissive color
+  Color emissive         = 7;
+}