change colors in vcg files

This uses a more pleasing very light blue background for blocks and adds
some comments on how the colors were defined with the hsv color model.

ir/ir/irdump.c

@@ -268,17 +268,18 @@ static void init_colors(void)
 
 	obstack_init(&color_obst);
 
-	custom_color(ird_color_prog_background,  "204 204 204");
-	custom_color(ird_color_block_background, "255 255 0");
+	// note: hsv values are in degree, [0,1], [0,1]
+	custom_color(ird_color_prog_background,  "204 204 204"); //hsv   0,   0, .8
+	custom_color(ird_color_block_background, "222 239 234"); //hsv 165, .05, .92
+	custom_color(ird_color_default_node,     "242 242 242"); //hsv   0,   0, .95
+	custom_color(ird_color_memory,           "153 153 255"); //hsv 240,  .4, 1.
+	custom_color(ird_color_controlflow,      "255 153 153"); //hsv   0,  .4, 1.
+	custom_color(ird_color_const,            "255 255 153"); //hsv  60,  .4, 1.
+	custom_color(ird_color_phi,              "153 255 153"); //hsv 120,  .4, 1.
+	custom_color(ird_color_anchor,           "255 153 255"); //hsv 300,  .4, 1.
+	custom_color(ird_color_entity,           "127 127 127"); //hsv   0,   0, .5
 	named_color(ird_color_block_inout,       "lightblue");
-	named_color(ird_color_default_node,      "white");
-	custom_color(ird_color_memory,           "153 153 255");
-	custom_color(ird_color_controlflow,      "255 153 153");
-	custom_color(ird_color_const,            "204 255 255");
-	custom_color(ird_color_phi,              "105 255 105");
-	custom_color(ird_color_anchor,           "100 100 255");
 	named_color(ird_color_error,             "red");
-	custom_color(ird_color_entity,           "204 204 255");
 
 	initialized = 1;
 }