mupdf patch from http://acidwords.com/posts/2016-07-26-hacking-mupdf-custom-background-colors.html

mupdf-bgcolor.patch

diff --git a/platform/x11/x11_main.c b/platform/x11/x11_main.c
index 21e3e84..3bce5aa 100644
--- a/platform/x11/x11_main.c
+++ b/platform/x11/x11_main.c
@@ -96,6 +96,8 @@ static char copyutf8[1024 * 48] = "";
 static Time copytime;
 static char *filename;
 static char message[1024] = "";
+static char *shadecolor = 0;
+static char *papercolor = 0;
 
 static pdfapp_t gapp;
 static int closing = 0;
@@ -129,6 +131,14 @@ static void showmessage(pdfapp_t *app, int timeout, char *msg)
 	}
 }
 
+static int colorasrgb(const char *name, XColor *color) {
+	XColor dummy;
+	if(XAllocNamedColor(xdpy, DefaultColormap(xdpy, xscr), name, color, &dummy))
+		return 1;
+	fprintf(stderr, "mupdf: couldn't allocate color '%s'", name);
+	return 0;
+}
+
 void winerror(pdfapp_t *app, char *msg)
 {
 	fprintf(stderr, "mupdf: error: %s\n", msg);
@@ -224,13 +234,17 @@ static void winopen(void)
 	xcwait = XCreateFontCursor(xdpy, XC_watch);
 	xccaret = XCreateFontCursor(xdpy, XC_xterm);
 
-	xbgcolor.red = 0x7000;
-	xbgcolor.green = 0x7000;
-	xbgcolor.blue = 0x7000;
+	if (!papercolor || !colorasrgb(papercolor, &xbgcolor)) {
+		xbgcolor.red = 0x7000;
+		xbgcolor.green = 0x7000;
+		xbgcolor.blue = 0x7000;
+	}
 
-	xshcolor.red = 0x4000;
-	xshcolor.green = 0x4000;
-	xshcolor.blue = 0x4000;
+	if (!shadecolor || !colorasrgb(shadecolor, &xshcolor)) {
+		xshcolor.red = 0x4000;
+		xshcolor.green = 0x4000;
+		xshcolor.blue = 0x4000;
+	}
 
 	XAllocColor(xdpy, DefaultColormap(xdpy, xscr), &xbgcolor);
 	XAllocColor(xdpy, DefaultColormap(xdpy, xscr), &xshcolor);
@@ -806,6 +820,8 @@ static void usage(void)
 	fprintf(stderr, "\t-H -\tpage height for EPUB layout\n");
 	fprintf(stderr, "\t-S -\tfont size for EPUB layout\n");
 	fprintf(stderr, "\t-U -\tuser style sheet for EPUB layout\n");
+	fprintf(stderr, "\t-D -\tshade color\n");
+	fprintf(stderr, "\t-P -\tpaper color\n");
 	exit(1);
 }
 
@@ -836,7 +852,7 @@ int main(int argc, char **argv)
 
 	pdfapp_init(ctx, &gapp);
 
-	while ((c = fz_getopt(argc, argv, "p:r:A:C:W:H:S:U:")) != -1)
+	while ((c = fz_getopt(argc, argv, "p:r:A:C:W:H:S:U:D:P:")) != -1)
 	{
 		switch (c)
 		{
@@ -854,6 +870,8 @@ int main(int argc, char **argv)
 		case 'H': gapp.layout_h = fz_atof(fz_optarg); break;
 		case 'S': gapp.layout_em = fz_atof(fz_optarg); break;
 		case 'U': gapp.layout_css = fz_optarg; break;
+		case 'P': papercolor = fz_optarg; break;
+		case 'D': shadecolor = fz_optarg; break;
 		default: usage();
 		}
 	}