Strange Editor Occurrance

I've a data structure for handling the books in a library in a game I'm making. It uses a script (C#) with the following top few lines:

public class BookHandler : MonoBehaviour, _BookTexture
{
public BookEntry book;
public _RandomColor randomColor;

Before I added the randomColor entry, the editor display showed a line for book as expected. However, once randomColor was added, the editor display still only shows the entry line for book and none for a second line for randomColor.

Both BookEntry and _RandomColor are ScriptableObjects

 

Continuing the saga: I created a new class that used the _RandomColor as a public variable and it doesn't show for it either.