Dyed Black Palm - Colour fading/darkening

[bear71]

I have a couple of handmade knives with Dyed Black Palm scales. I love the appearance and feel of the handles and they are a part of my regular rotation. As time has gone by the color of the dye that the wood took in the lighter sections has started to fade or darken in most areas. I have tried lightly scrubbing the scales with mild soapy water and a firm toothbrush but this has had no effect, I didn't want to go more abrasive before I asked advice. Anybody know if the colour can be brought back and if so how? I guess this also applies to some other stabilized wood scales that have darkened/become less vibrant with age.

Cheers,

Jules