Hi.
Just adding this in case another user has come across this situation.
In LO 5.3.3 Writer I found I could not change the palette or edit any colours in Table>Properties>Background. The only choices were from a set palette (later found to be named named standard.soc)
Some searching and it is an issue with 5.3+ being worked through.
The colours available from the palette were not suitable and I wished to change a kaky Brown to light green.
I found with a file search on my machine the LO install placed standard.soc in /usr/lib64/libreoffice/share/palette/standard.soc
Opening the text file I saw my there was no Brown but also found I had another standard.soc ~/.config/libreoffice/4-suse/user/config/standard.soc
This did contain the kaky Brown. This file is 3 years old and as I have done 4 distribution updates in that time I can't be sure where it came from, but on an install of LO5.3 on a new machine the file is not in ~/.config/libreoffice/4-suse/user/config/
I found by copying a palette to ~/.config/libreoffice/4-suse/user/config/ and naming it standard.soc I could edit the file and change colours (in simple RGB hex) or add a new colour at the end of the file to have a colour I wanted available in Writer tables. This new changed palette will also become the standard palette for you in other areas of LO. You could of course edit /usr/lib64/libreoffice/share/palette/standard.soc but that will change the palette for all users and require root privileges.
steve