Brian Baylis had this to say about Celeste:
The Bianchi paint color varies a bit no matter what period you are talking
about up until the "modern" era. Most of us have the color matched and
formulated in various paint brands to match something on hand. After than,
it either goes on like it is or can be adjusted to some degree. The main
problem is that what the owner of the bike has in their minds eye may not
be what the painter envisions; depending on how ridiculously fussy the
client is.
give the above, you might want to either take your bike to an automotive painter to have a paint match done, or start calling local frame painters.