Layer/Outline Custom Colors do not Save

The color of the outline of paths/objects, when I have changed them to custom colors (ones not listed in the dropdown menu in "Options for 'Layer Name'"), revert to black the next time I open the file.  For example, I opened the options pop-up for a layer called "refs" containing two objects, clicked on the colored square beside the dropdown menu of colors to launch the color picker, input RGB values for the specific color I wanted, then selected "OK" twice to save these changes.  The "refs" layer displayed the color I chose, and so did the outlines of its objects on the Artboard when I hovered over them.  However, even after saving changes and exiting the program correctly, the custom colors were not remembered upon reopening the file.  Any layer color with a custom value had reverted to default "Black," from the dropdown options.