I have considerable experience with osage. It is my opinion that the darkening of this wood UV only. I have several items around the shop I made from osage. One is a box I made for my sharpening slips. I made no effort to control the bright yellow color. The inside and bottom of this box is still "highliter yellow" while the outsides are now brown/orange. I also made a handle for one of my lathe tools which I finished with CA and it is still bright yellow. I don't get too hung up on this matter as both colors are attractive.