Simplify determine_colors more
Simplify determine_colors more

Get rid of reverse argument.  Also "xor" instead of "or" selection mode
with reverse mode.  Selection works with reverse mode now.  Before, it
didn't render.

asivokon/vte-fx,asivokon/vte-fx,pjm0616/vte,gloob/vte-copy,jessevdk/vte,flaxandteal/gasket-vte,jessevdk/vte,rvu95/vte,gloob/vte-copy,aligo/vte,flaxandteal/gasket-vte,saitoha/vte-sixel,aligo/vte,asivokon/vte-fx,thestinger/vte-ng,rvu95/vte,saitoha/vte-sixel,pjm0616/vte,aligo/vte,rvu95/vte,rvu95/vte,jessevdk/vte,asivokon/vte-fx,flaxandteal/gasket-vte,thestinger/vte-ng,gloob/vte-copy,thestinger/vte-ng,saitoha/vte-sixel,pjm0616/vte,flaxandteal/gasket-vte,jessevdk/vte