graphite color support missing support for longer colors (results in no colors set)

[keen99]

https://github.com/etsy/dashboard/blob/master/htdocs/phplib/GraphFactory.php#L410

here we're restricting our match only to color codes that are 6 characters long - but shorter and longer colors are valid for graphite.

https://github.com/etsy/dashboard/blob/master/htdocs/phplib/GraphFactory.php#L413

then, if we failed that condition, we just leave the color unset, resulting in:
&colorList=

in our graph uri...

would be easy enough to accept a shorter/longer code, trigger an error/warning when an unacceptable code is sent, and/or select a random color from the list instead....