wsconscfg(8) has an example how to set a vt100 terminal emulation
Code:
EXAMPLES
Configure screen 1 (i.e., the second) for type ``80x50'' and VT100
terminal emulation. (Note: ``80x50'' is a screen type offered by the
vga(4) display driver. In this particular case, an 8x8-font must be
loaded beforehand to make the screen useful. See wsfontload(8).)
# wsconscfg -t 80x50 -e vt100 1
Terminal types like
vt100 are defined in
/etc/termcap The codes used to define the capability of a terminal type, including setting foreground and background color are explained in
terminfo(5)
So you would have to edit
/etc/termcap of the terminal type used by the OpenBSD console terminal. IIRC that is vt220.
But this all seems to be very difficult. Before attempting to change the background and/or foreground color with this method, you could try to create a file with the ANSI escape sequence to set the foreground to say green and simply use
/bin/cat to display the file and see whether that is sufficient to change the foreground or text color. See
https://en.wikipedia.org/wiki/ANSI_escape_code for info about these codes.
Of course that would require a change to one of the ANSI terminal types mentioned in
/etc/termcap
I have to file my income tax return before April 1st, so I don't have time to investigate this any further. It is a pity, checking this color thing out is more fun, than filling a tax return