How to represent missing colors in a search result facet

In our online store we have a facet to filter the search results by color. The different values for this filter are displayed as a small tile according to the name of the value. The color of the tile is derived from the name of the color, f.ex. red => #FF0000. It currently looks like this:

enter image description here

Some items have weird values for the color attribute, f.ex. orange/grey or oak. We have a translation map where can add the color manually, but it might take some time until the new values are added to this map. Until this happens we don't know which color code to assign to this tile so we display a question mark:

enter image description here

User feedback has shown that the question mark is perceived as a bug rather than a missing color.

What could be a better way to display this, without confusing the user but also making it clear to our staff that there is a color missing?

Some options we have discussed:

  • A friendlier icon
  • The good old "image missing" icon some browsers use

EDIT: Another option:

  • For missing colors, display a text link instead of the color tile, below the color grid

enter image description here

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