I dont mean to make this sound difficult as it is not. Anyone can do it and it dont look half bad.
Here's what you need
Dark walnut stain, mahogany stain and light walnut with polyurethane in it. The latter is thinner and a little sticky which helps blend or bleed the colors together.
3 strips of cloth 1/4' wide and 10" long or so.
And a scraper of some fashion.
1st Dip the center of one cloth in the darkest stain. Apply the cloth strip to the bows backing while holding each end of the cloth in your hands. One strip about every 3" to 4" or so.
Start at the handle and work out towards the tips.
2nd - Center the next darkest color between the first bands of dark color. Your first few bands will be thick and may want to run. Avoid this by going back every few bands and retouch the thick areas so they dont run.
3rdly - Take the light poly stain between each color before. Then place another row of dark bands over the lightest color and beside the darkest color. You don't have to be perfect or have an exact pattern from here on.
4th and final is repeat starting over with the darkest color & placing dark next to a lighter color. Go to the next color and the next keeping from placing the same colors side by side,,, which would just make the band of color wider.
As your cloth's start to dry out a bit use the poly'd cloth with the lightest color to go over all the colors, directly over them, blending them together. It should start looking like this.
Dip the poly stain rag again and just keep going up and down the limb on each color and between blending them all together.
End result leaves messy looking edges.
To take care of the uneven trim and runs, use a scraper to clean up the lines. Best to do this after it is completely dry to avoid any wood shavings in your finish.
Once the stain dries for a day or so you can apply a clear finish or satin depending on you.