Cocobolo darkening question

[Hengelo_77]

Here are two pictures of the same handle made out of cocobolo.
The first one when it was just finished, the darker and second one a few years later.

At the moment I am working on a knife with a handle out of the same piece of cocobolo as this handle came out of.

Is there a way to prevent this darkening?
Or is there a way to speed up this proces?
The reason I ask is that the knife I am working on now, when it is finished I'd like it to have it's final colour (the same now as in so many years)

Fresh cocobolo:

Same handle after a few years:

 

[Jason Fry]

Put it in direct sunlight and it will darken. UV is what makes it do that.

 

[Stacy E. Apelt - Bladesmith]

UV and O2 are what changes the color of wood. Exposure to warm air and sunlight will darken most all photochromic woods. Make sure the handle is evenly exposed on all sides.