The glory... the glory!

Smaug was really enormous, though not as much like famous Ancalagon the Black. He was of reddish golden color [ which harmonized very well with all the gold he gathered in Erebor, ha ].

He was puffing smoke from his nostrils and maw, though during sleep, the fire barely smoldered in his insides.

As Tolkien himself said [ more or less, as I read polish version of The Hobbit ]

"Smaug lay with folded wings like a huge bat, turned a little sideways so that the hobbit could see his body from underneath: a long, pale belly sprinkled with precious stones and gold crumbs that had pierced his skin from constantly lying on this bed of riches."

In the movie, voiced by Benedict Cumberbatch [ who did great job! ], Smaug seemed even bigger than on Tolkien's own drawings. He was of more earthy colors, though lighted by fire, he looked really like shining with golden scales.