If you have any woodstain, (any of the brownish colours, not bright blue, green or red, obviously) mix a little of it with a jam-jar full of white spirit (or even turps substitute) and brush it on thinly.This dilute solution should soak into the surface of the wood and darken it slightly without giving it a shiny surface. Second and third coats can be added if you want to darken it further.

Cuprinol oak stain wood preserver gives a good natural colour.