Steps to Reproduce:
- Open https://en.wikipedia.org/w/index.php?title=Template:Ordered_list/styles.css&action=submit (a nonexistent document)
- Add * { background-color: #aaaaaaaa }
- Click "Show Preview"
Actual Results:
Invalid or unsupported value for property background-color at line 1 character 23.
Expected Results:
This is a widely supported syntax, it should be supported.
This is supported by Color 4, as of April 2022 a W3C working draft.