You can create a your own palette file,
- with .soc extension
- and with a content like the following:
<?xml version="1.0" encoding="UTF-8"?>
<ooo:color-table xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" xmlns:draw="urn:oasis:names:tc:opendocument:xmlns:drawing:1.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:ooo="http://openoffice.org/2004/office">
<draw:color draw:name="panna" draw:color="#faf7d2"/>
<draw:color draw:name="mattone" draw:color="#bc5a1f"/>
<draw:color draw:name="OldLace" draw:color="#FDF5E6"/>
<draw:color draw:name="Cornsilk" draw:color="#FFF8DC"/>
</ooo:color-table>- then you have to put it (also as symlink) in /libreoffice/share/palette.
You will be able to choose that palette (with the same name of the file .soc), and you will be able to use your preferred colors highlighting words in LibreWriter, for example.