If your font colour is always used in some specific context, e.g. for trademark, character name, technical word, … or full comment paragraph, the best solution is to include the font colour in a user-defined character or paragraph style.
Thus there is no longer any issue with the recent colour list.
In addition, when this colour setting is shared among several documents, put all your definitions in a template file (extension .ott) and base your documents on this template. This also allows you to change this colour in all your documents simply by modifying the template without the need for any other “patch” in the documents themselves.
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