Fixes drop-shadow recognition to accept all colors

* Did not support half of all properly formed hex values ([#0-9a-zA-Z])
* Did not support w3c color names ((red|green|...))

Don't have time to do it now, but the best solution would be to tokenize each parameter and compare it against a shared regex for the appropriate type (e.g. the first 3 properties against a length regex, the fourth against a color regex, and so on).