The color is celeste. It's the color Bianchi racing bikes, and by extension, many other Bianchi bikes, are associated with. Celeste and Bianchi are almost synonymous.

The color must remain celeste. No other color would be as appropriate on that bike. No other color will be as valued by Bianchisti.

Furthermore, the tubing is Columbus tubing, so you will want to re-badge the bike with the Columbus decal, at a minimum. Really, the proper way to approach this is to strip the frame of all rust, prime it, and repaint it in the original celeste. Apply framesaver to the inside of the frame. Commission a set of decals to replace the decals that will be damaged by the stripping & painting process. After it's been repainted, apply the new decals. Clearcoat over that is optional.