I can give you some background on yew wood having worked with it quite a bit in a former life as a furniture builder. There are two types - European and Pacific. I imagine the Proacs use the European "version". Yew was highly prized for making longbows in England and France and became quite rare for a time. The Pacific genus is also not found in abundance and is priced accordingly.
Both kinds have reddish to orange heartwood with much lighter sapwood (sometimes almost white). The sapwood is what I see on most speakers. Either heartwood or sapwood will darken some with age and exposure. Yew is actually a softwood (evergreen). It is one of the "hardest" among the softwoods, though, and takes a good polished finish. As a softwood, Yew contains more oils than the hardwoods usually used in speaker cabinets. As such, you can expect darkening - the degree to which is usually governed by the thoroughness of the drying process.
Hate to be the bearer of bad news but I doubt, from my experience, that your will ever see a "matching" of the wood that has aged. It will even out some but will never match without being "touched up" with stain. Don't know how long the exposed portion has been so exposed but if it is on the order of a year or two "a couple of months" will not result in anything close to a match. I would advise against staining, however, because that portion will not subsequently match in the long-term. Let me know if you would like to know more about yew (not you!).
Both kinds have reddish to orange heartwood with much lighter sapwood (sometimes almost white). The sapwood is what I see on most speakers. Either heartwood or sapwood will darken some with age and exposure. Yew is actually a softwood (evergreen). It is one of the "hardest" among the softwoods, though, and takes a good polished finish. As a softwood, Yew contains more oils than the hardwoods usually used in speaker cabinets. As such, you can expect darkening - the degree to which is usually governed by the thoroughness of the drying process.
Hate to be the bearer of bad news but I doubt, from my experience, that your will ever see a "matching" of the wood that has aged. It will even out some but will never match without being "touched up" with stain. Don't know how long the exposed portion has been so exposed but if it is on the order of a year or two "a couple of months" will not result in anything close to a match. I would advise against staining, however, because that portion will not subsequently match in the long-term. Let me know if you would like to know more about yew (not you!).