I made a bow for my son out of a piece of scrap.  I like the look of aged osage, but I think the fresh neon yellow would be more alluring to a child.  Does anyone have experience with UV-inhibitor finishes that might at least delay the inevitable honey brown coloring?

I don't think you can keep it yeller. I have osage bows that stay in my utility room most of the time and they still turn darker with time. You could paint the bow with yellow paint to achieve the look you want.     Pat

I think the darkening over time is going to happen.  I think the only thing you can do is prolong it by keeping them in the dark.  I have an osage duck call that is 15 or so years old.  The exterior has turned darker but if you pull it apart the insert has a clear line where dark and much lighter colors meet.  The part exposed to light is dark and the part hidden inside the call still retains the brighter color.  Not as bright as when new, but close.

Like said above I don't think you can keep it as yellow as when you first made it.But for me I think that is the beauty of osage,it darkens to a beautiful aged color.