Tidy question about the config args

I have a question about using the $config arguments with tidy_parse_string() and tidy_repair_string() etc. The functions seem to totally ignore new-blocklevel-tags new-empty-tags new-inline-tags E.g., I have in my config array some custom tags [new-inline-tags] => blue,bold,green,italic,red,underline I feed this string xxxx<green>xxxxxxx</green>xxxxxxxxx to tidy_parse_string() and get this report from the tidy_get_error_buffer() line 1 column 5 - Error: <green> is not recognized! line 1 column 5 - Warning: discarding unexpected <green> line 1 column 19 - Warning: discarding unexpected </green> PHP does not report any errors. What's the point of having new, custom tags if functions ignore them? What am I missing? Thanks.........