Add notes on NO_COLOR environment variable to the manual

docs/content/manual/manual.yml

@@ -168,6 +168,8 @@ sections:
         By default, jq outputs colored JSON if writing to a
         terminal. You can force it to produce color even if writing to
         a pipe or a file using `-C`, and disable color with `-M`.
+        When the `NO_COLOR` environment variable is not empty, jq disables
+        colored output by default, but you can enable it by `-C`.
 
         Colors can be configured with the `JQ_COLORS` environment
         variable (see below).

jq.1.prebuilt

@@ -112,7 +112,7 @@ Use the given number of spaces (no more than 7) for indentation\.
 \fB\-\-color\-output\fR / \fB\-C\fR and \fB\-\-monochrome\-output\fR / \fB\-M\fR:
 .
 .IP
-By default, jq outputs colored JSON if writing to a terminal\. You can force it to produce color even if writing to a pipe or a file using \fB\-C\fR, and disable color with \fB\-M\fR\.
+By default, jq outputs colored JSON if writing to a terminal\. You can force it to produce color even if writing to a pipe or a file using \fB\-C\fR, and disable color with \fB\-M\fR\. When the \fBNO_COLOR\fR environment variable is not empty, jq disables colored output by default, but you can enable it by \fB\-C\fR\.
 .
 .IP
 Colors can be configured with the \fBJQ_COLORS\fR environment variable (see below)\.