Change the default color of null to Bright Black

docs/content/manual/manual.yml

@@ -3656,7 +3656,7 @@ sections:
         - color for object keys
 
       The default color scheme is the same as setting
-      `JQ_COLORS="1;30:0;37:0;37:0;37:0;32:1;37:1;37:1;34"`.
+      `JQ_COLORS="0;90:0;37:0;37:0;37:0;32:1;37:1;37:1;34"`.
 
       This is not a manual for VT100/ANSI escapes.  However, each of
       these color specifications should consist of two numbers separated