Description:
With direct formatting, when two different types of underline (e.g. single, double, bold, dotted, dash, etc.) overlap, the second underline will not use the same color as the text.

Steps to Reproduce:
1. Start Writer in safe mode
2. Create a new document
3. Increase the font size (to make the color difference more obvious)
4. Write some text (e.g. "This is a test")
5. Select the first word (e.g. "This") and underline it with a single underline (e.g. Ctrl+U)
6. Select some text overlapping with the first word
   * For instance, select its last letter and the next two words (e.g. "s is a")
7. Underline the selection in `Bold`
   * i.e. click on the `Underline` icon drop-down button and select `Bold` in the menu

Actual Results:
The bold underline appears with a different color (in my case blue, but sometimes it's also green) than the text (in my case black, since this is the default color)

Expected Results:
The bold underlining should be the same color as the text


Reproducible: Always


User Profile Reset: Yes

Additional Info:
I found a workaround : when underlining the overlapping text, if I first underline it with a single underline and then underline it with the other type of underline, then the color remains the same as the text.

To be noted that the bug also occurs when the two underlines are the same type, unless the first underline is a single one (e.g. in the procedure, underline both times in bold and the bug still occurs).

Below are my system details:

> Version: 25.2.6.2 (X86_64) / LibreOffice Community
> Build ID: 520(Build:2)
> CPU threads: 8; OS: Linux 6.14; UI render: default; VCL: gtk3
> Locale: en-US (en_US.UTF-8); UI: en-US
> Ubuntu package version: 4:25.2.6-0ubuntu0.25.04.1
> Calc: threaded