Q: Does the Silver Dragon count towards your chain of seven dragons?

A: The Silver Dragon starts out Wild, just like the Rainbow Dragon. In this state, it counts as all colors all the time. Later it will reflect the color of the Action on top of the discard pile, at which time it is to be counted as a full panel of that color.

Either way, it certainly counts towards your win (as long as it is your color, or wild – obviously, if it is currently not your color, then it can’t be connected with any group of your color).