The Gray thumb for RadCalendar is fixed now, thank you.
As for the skin itself - well, yes, it is not exactly the same as Default2006 and it should not be. When creating the Gray skin, we tried to make a skin with a modern look, which is a little more usable than Default2006 and has more contrast.
As with all other skins, you are free to modify it by using some custom CSS rules together with the embedded skin, use the old Default2006 skin as a non-embedded skin, or created a custom skin based on one (or both) of these skins.
the Telerik team