cherry will darken when exposed to sun. so if you leave it out in the bright sun for several days it will darken.

You can also try the Cherry Lye treatment, see link below.

Here is a link that might be useful: Cherry Lye treatment

I've used the lye approach, with mixed results. I term it the "ready, fire, aim," approach as you can run some samples using different concentrations, but when it's time to apply, you apply and get what happens.

I have had good results with applying a coat of boiled linseed oil, and letting set in the sun for a few days. Let the BLO cure for at least a week. Then apply an oil-based varnish over the top. I have a chest that I did earlier this year that looks like it's 20 years old. When I get home on Monday, I can post a photo if you like.