S&W front sight help?

Is the front sight on the 686 the pinned version?? If so then you can get a few different style sights to replace it with. SDM sells a gold bead and also a fiber optic version. If it is a 686 where the front sight is part of the barrel, then it gets a little more involved. They do sell a kit I believe that allows you to replace the orange insert material with a different colored plastic goo that hardens in place of the old one. Other than that, you would have to have your barrel machined to the current style where the front sight is pinned in place, or the like some models where it is held by sping pressure (ala Weigand/DX models), or just dovetailed. I went the dovetail route on my 586 as it was the cheapest way to go...about $60 from my gunsmith.

Sheldon is correct. There are 2 ways to replace the sight insert that are or were available from Brownell's. (1) there was a kit with colored plastic sheets which have an insert cut out by the whoever is doing the replacing and filed to fit the cut in the sight and inserted. (2) there are kits where the resin is mixed up and a dam put on each side of the sight and the resin poured in which then hardens. The gunsmiths I know seem to use #2. Either method offers a variety of colors so one can pick what works best for them. The gunsmiths around my area charge $20-30 to do this. This is probably the least expensive route to take however you may want to consider the alternatives that Sheldon offered.

If the front sight is a non-replaceable fixed blade and you have a local gunsmith, he can replace the insert with a fresh one.
If the front is on a newer 686 with a replaceable front sight blade I would recommend having the gunsmith replace the old front with a fibre optic version.
If the gunsmith has a fully equipped shop, he can mill the older revolver for a replaceable blade sight too though this would cost quite a bit more money.

Brownell's used to sell a kit for replacing or inserting the color insert on the front sight. I'm not sure if they still sell it but I'm sure it is available somewhere. You would have to pull out existing insert and clean the dovetail, mix the epoxy, fit it to the dove tail and shape it once it has hardened. The kit came with excellent instructions and is a simple task.

It looks like they have something a little different now:

http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=397

IIRC, Novak's used to do a mod where they would mill a dovetail into the sight ramp and use a dovetailed replacement blade.