The Linux console has some bugs with bright colours. It seems likely

The Linux console has some bugs with bright colours. It seems likely
that it is emulating them by setting a bright (or bold) flag; however,
when the colour is changed from a bright colour (say SGR 96) to a
non-bright (say SGR 36), the flag is not reset, so the new colour
remains as bright. SGR 39 (default colour) also does not reset, so you
end up with the bright default colour. Work around this by sending SGR 0
when switching away from a bright colour, and disable AX for TERM=linux.
Also make the check for AX simpler and do not check for the op
capability is not actually used. GitHub issue 3976.