runtime(colors): don't unnecessarily reload v:colornames dict

fixes: #14234
closes: #14235

Signed-off-by: Alin Mr <almr.oss@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index e3a9f20..f2ff3a8 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 9.1.  Last change: 2024 Feb 08
+*eval.txt*	For Vim version 9.1.  Last change: 2024 Mar 20
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2076,6 +2076,10 @@
 		both automatically load all `colors/lists/default.vim` color
 		scripts.
 
+		You can make changes to that file, but make sure to add new
+		keys instead of updating existing ones, otherwise Vim will skip
+		loading the file (thinking is hasn't been changed).
+
 				*v:completed_item* *completed_item-variable*
 v:completed_item
 		|Dictionary| containing the |complete-items| for the most