I modified the Text Body style, too. Yet when I apply this style to a paragraph by clicking in the paragraph and then double clicking Text Body in the Styles list, I get something else entirely.
This happens to with some Heading styles, too, that I modified. What gives here?
You may have some direct formatting applying to that text parts. Direct formatting means applying format changes using the bold/italics/underlined buttons from the tool bar, for example. That text will keep its styles-defined formatting, but the direct format will override it, even if you change the complete paragraph to another paragraph style.
To make sure that LO just applies the paragraph styles, you will have to remove direct formatting manually, To do so, just select the paragraph and select Menu “Format” → “Clear direct formatting”, or hit “CTRL+M”.
Another possible source for divergent format definitions are “Character Styles” - they apply only to selected characters, not to complete paragraphs.
I found the problem, I think. I selected the whole text and when to Format > Character. In Font Effects, I chose Automatic. For some reason unknown to me, some of the text was set to Red 2. In previous attempts to correct this, I selected some text of the same paragraph style, chose Copy Format, and wiped this into the red text. That made in black again, but every time I reopened the document, there was the red again. Now, after going to Automatic, everything works correctly and is displayed correctly. I have no idea where the Red 2 came from.