I am refinishing a floor, but there is new maple being installed alongside 20 year old maple. The problem with this that the old maple, even after it is sanded, will probably be a little darker than the new maple. Is there a way to tint the new maple to more closely match the aged patina of the old wood, so that when we refinish everything comes out the same shade?
I think you are right, the old maple will be darker than new maple after refinish. Problem will be less with water-base finish than with oil-base.
I have faced this problem many times on restoration of ash and beech wood. If I add patch of new wood colors can be similar after sanding but old wood is darkened much more by finish, even shellack. Linseed oil darkens much more.
Dye or stain is immediate fix, maybe you won't like it in some years. If you dye new wood to color of old wood new will become darker in 5-10 yrs: dye + age + finish vs. age + finish. And I understand that maple dyes unexpectedly.
Solution when you cannot wait for light to have its effect naturally which takes too long, you can age the new wood.
Antiques books speak of using wood ash water to make new wood look old. Also sometimes used to make fakes! You cannot buy wood ash any longer I think and making from scratch is not reliable. But chemistry informs us this makes alkali solution so we may use sodium carbonate Na2CO3 instead and it can be purchased anywhere.
I don't know how effective this works on maple you will have to test on scrap pieces. I have used it on pines, fir, oak and some type of mahogany and all become darker. Works better on hardwoods, and bonus for mahogany it becomes more red. Dilution or number of coats control effects.