Over time the factory sights on a model 27 or 28 ...haven't really bothered me - even as my 65 yr old eyes are not getting any better. Sure, it could be modified..but that will detract a little from what the model 27's and 28's really are..a great classic N frame. Model 27's and 28's are my all time favorite revolver - especially the older 27's in Nickel.
You can find a "model Paint" set sold in a lot of gunstores...with about 9 different colors in them ....white, day glow yellow, day glow green, orange, etc.../ they will all come off if you get any cleaning solvents near them...but if the sights really drive you crazy, try the paint.