Make object key color configurable (close #1739, #1791, #2638)

Co-authored-by: David Haguenauer <ml@kurokatta.org>
Co-authored-by: Eric Pruitt <eric.pruitt@gmail.com>

docs/content/manual/manual.yml

@@ -3485,9 +3485,10 @@ sections:
         - color for strings
         - color for arrays
         - color for objects
+        - 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"`.
+      `JQ_COLORS="1;30:0;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