replace cyan and yellow which not easy to read on white background (#1903)

* replace cyan and yellow which not easy to read on white background

* wallet output color scheme configuration for terminal dark/white background

* use true for dark_background_color_scheme to make the default behavior same as before

config/src/comments.rs

@@ -344,6 +344,12 @@ fn comments() -> HashMap<String, String> {
 		"data_file_dir".to_string(),
 		"
 #where to find wallet files (seed, data, etc)
+".to_string(),
+	);
+	retval.insert(
+		"dark_background_color_scheme".to_string(),
+		"
+#Whether to use the black background color scheme for command line
 ".to_string(),
 	);