In high color modes it is always clear how white is set with vga_setrgbcolor(3). In the other modes you need vga_white().
However, it only knows about the default palette. If you change it with one of the palette functions the function will not know about it.
svgalib(7), vgagl(7), libvga.config(5), vga_init(3), vga_setmode(3), vga_setpalette(3), vga_setpalvec(3), vga_getpalette(3), vga_getpalvec(3), vga_setcolor(3), vga_setrgbcolor(3), vga_setegacolor(3)
This manual page was edited by Michael Weller <firstname.lastname@example.org>. The exact source of the referenced function as well as of the original documentation is unknown.
It is very likely that both are at least to some extent are due to Harm Hanemaayer <H.Hanemaayer@inter.nl.net>.
Occasionally this might be wrong. I hereby asked to be excused by the original author and will happily accept any additions or corrections to this first version of the svgalib manual.