I finally got the quilted maple veneer on the headstock and body to the point where I'm happy. It's sanded up to 2000 grit and has ~30 coats of Tru Oil. It's only at this point that I step back and notice that the veneer on the body has turned a not unattractive shade of yellow while the headstock veneer remains unchanged.
I'm perfectly happy with either shade. I'd just like them to match. Any suggestions?
It's happened because they are different bits of wood. You can't guarantee exactly the same results from natural products unless they are pieces from the same part of the same tree. If the quilted veneer was added to the headstock at the factory, it's very unlikely it's from the same but used for the body.
As Tru Oil has a yellowing effect, I'd keep on adding more layers to the headstock, and no more to the body. On the other hand, I much prefer a headstock that doesn't match the body colour.
Alternatively, you could add a drop of a yellow dye (not water-based) into a small amount of Tru Oil and wipe that on the top. Don't add much or it could go very yellow! Better to have to do it in 2 or 3 layers than have it too bright. Then you'll need a few more Tru Oil layers over the top of that as you'll need to sand back again and you don't want to sand off the yellower finish!