message: Use StructureState for color index instead of generic size_t.
  Color indices are represented by StructureStates.
diff: #pragma once
  #include "Core/ListBoxBase.h"
  +#include "../Common.h"
  #include <NAS2D/Signal.h>
  @@ -26,7 +27,7 @@ public:
  public:
  Structure* structure = nullptr; /**< Pointer to a Structure. */
  std::string structureState; /**< String description of the state of a Structure. */
  - std::size_t colorIndex = 0; /**< Index to use from the listbox color table. */
  + StructureState colorIndex = StructureState::UNDER_CONSTRUCTION; /**< Index to use from the listbox color table. */
  };
  public:
  