Here's my 64 with an orange front sight I painted:
It is frankly FANTASTIC and makes the front sight pop. Much better than the stock silver on silver. I used a coat or two of Testor's flat white enamel followed by a coat or two of Testor's fluorescent orange enamel. Has held up swell and makes a night and day difference in front sight acquisition in low light and with different backgrounds or just during the day. Highly recommended little mod, many people do this and for good reason. Easily removable with paint thinner and a toothbrush if you don't like it or want to sell the gun.
Ensure a good dry time between coats, make sure you degrease the sight before painting, allow a good dry time (a few days ideally) between coats. Really no downsides, I'd do it. In fact I've a 67 that might get painted tonight...