Weird issue with overridden heading colours

[rmwiseman]

Version, Operating system
1.2.0 on Linux Mint 22 (using X11 not Wayland).

Describe the bug
Sometimes I want to include text from elsewhere, including headings and formatting. I like to paste as-is and then make all the text green so that it stands out and it's clear that it's from elsewhere.

I've noticed some weirdness with colours, however. When I select the text and make it green, some headings are correctly changed but others stubbornly remain the same colour. It seems to be to do with BOTH the colour AND the heading level, though!

Green text: headings 1, 5 and 6 become green; others don't.
Yellow text: headings 1, 2, 5 and 6 become yellow; others don't.
Orange text: all headings become orange.

To Reproduce
Steps to reproduce the behavior:

1. In a note, create a few lines of text.
2. Highlight the text and change the colour to green (or whatever).
3. Place the cursor on one line of the coloured text and cycle through the different headings using Ctrl+1 to Ctrl+6.
4. See how some of them consistently keep their default colour but others obey the new text colour.

Screenshots
Here's a screenshot related to the colours I mentioned above:

(Yes, my heading 6 looks the same as normal text.)

I produced this by typing out the text once, colouring it green, setting the heading lines using Ctrl+1 etc., then copying, pasting and colouring it twice.

For reference, here's the same text with colour removed:

(I don't know if it's significant, but I have noticed this kind of behaviour before, I think with code blocks. Perhaps it's related.)