If ALL you're looking for is a 'brown color' .... wash the teak with TriSodiumPhosphate (TSP) to dissolve the UV destroyed surface cells ... the 'grey'. TSP is obtainable in a hardware/paint store. Just mix with water, or make a paste, apply and let soak ..... then scrub off the grey with soft bristle brush.
Then immediately apply a 'sealer' such as SEMCO, Teak Wonder, etc. etc. etc. ... sealers usually need to be reapplied every 6 months to prevent the UV damage.