I'm always suspect of the numbers stamped on Bianchi's but this frame would definitely be right around '73 (IMO) based on what details are shown. The seat-stay tops were done like that until about '75-'76. The lack of shifter braze-on's would make it pre '74 or so.

I have no idea on the color. I would think not original, but would tear the bike down and look for signs of a re-paint. The fork (if original) was originally painted, with maybe just the drop-outs left exposed. Some better photos of the frame details would help.

There was a clean '74 on ebay recently, try searching the sold listings for that as I remember it having a lot of good photos.