Any way to touch-up brown spots on board?

i have a nice old board that is in pretty good shape–the deck looks a little aged, which is fine. But there are several brown spots where water has gotten into the foam a bit over the years. I know I could just leave it as it is, but the spots draw my eye when I look at the board and I’d like to try to make them less noticeable. Is there any good way to touch them up?  I thought of maybe using water-based acrylic paint to try to blend in and match the surrounding deck color, and then go over with a resin topcoat. Anyone tried this?

 How big an area are you talking about ?

I’ve used a Dremel with thin bit and bleach but you have to drill holes every 1/4 in.

 

They are several fairly small areas, maybe an inch or two big, either long or round-shaped.  Bleach might be an idea, but I still need to end up with something that will match the rest of the deck (it’s an old poly board which was originally clear, now it aged a bit and  lightly yellowed).  Getting the brown spots touched-up so that it matches the lightly yellowed deck may be just too difficult to do.