The color split and group buttons (font color, background color, highlight color) in the Formatting toolbar loose their settings when the LibreOffice window is smaller than the toolbar and if you have to click at the toolbar arrow to make the other commands visible that are outside of the window.
Steps to reproduce:
1. Open Calc or Writer.
2. Set a custom font, background and highlight color via toolbar commands.
3. Shrink the window size so that these commands are not visible anymore.
4. Click at the arrow at the right of the toolbar.
Custom settings are gone and the default colors are available.
Settings are persistent and the custom colors are available.
Tested with 22.214.171.124.alpha0+ from 2018-12-04_00:57:42 and with 126.96.36.199.
Thank you for reporting the bug. I can confirm that the bug is present in
Build ID: 86daf60bf00efa86ad547e59e09d6bb77c699acb
CPU threads: 2; OS: Windows 6.1; UI render: default;
Locale: en-US (en_US); Calc: group threaded
Not reproduced in
Build ID: 3ca42d8d51174010d5e8a32b96e9b4c0b3730a53
Threads 4; Ver: 4.15; Render: default;
Looks like something related to my work on Bug 42029. The overflow popup is now implemented as a separate toolbar, so now it has the same problem as other toolbars - see Bug 113433 (i.e. closing and reopening the formatting toolbar will give the same results).