When you proof your B17 does the colour change? Ie would the honey coloured one darken?
Absolutely. After 20 minutes in neatsfoot oil my honey B73 turned an even midbrown, a colour it would approach only unevenly after several years of Proofide and perspiration.
You may ask why order a honey saddle (and grips, which I gave the same treatment) only immediately to darken them with neatsfoot oil. The answer is that the result is a lighter, even, dark tan than the Brooks factory brown, with greater depth to the color. I'm an artist so I'm sensitive to such distinctions.
I wipe the saddle lightly with the Brooks Proofide once or twice year to maintain protection because whatever oil or wax sinks in during a relatively short period for colouring a new saddle doesn't give permanent protection.
You can't soak it very long, say 12 hours or a whole day, without softening the leather, though there is a school of thought, of which I heard from the famous late American mechanic Sheldon Brown, which believes that instant break-in can be achieved by soaking a Brooks saddle for 24 hours in motor oil.)