nestlog: bugfix: color_off() must use CE_Ansi instead of CE_None

include/nestlog/color.hpp

@@ -118,7 +118,7 @@ namespace xo {
     inline color_impl<int>
     color_off() {
         /* any non-zero value works here for color */
-        return color_impl<int>(CF_ColorOff, CE_None, 1 /*color*/, 0);
+        return color_impl<int>(CF_ColorOff, CE_Ansi, 1 /*color*/, 0);
     } /*color_off*/
 
     template <typename Contents>

include/nestlog/log_state.hpp

@@ -211,6 +211,14 @@ namespace xo {
         this->ss_ << ee_label;
 
         if (log_config::nesting_level_enabled) {
+            /* e.g.
+             *   (^[[38;5;195m7^[[0m)
+             *    <-----a---->b<-c->
+             *
+             *   a = color on
+             *   b = level - displayed in color
+             *   c = color off
+             */
             this->ss_
                 << "("
                 << with_color(log_config::encoding,