Definitly go with a neon -- whether actual site paint or nail polish. I would also like to recommend green or bright yellow. It picks up pretty well in daylight, but is also easier to pick up when it get dark as compared to red, etc.
Good timing on this question. Recently I've been experimenting with colors for the sights on my wife's PT22 and the rear sight nubs on my Judge. I first tried some bright red, it didn't show up enough so I went with white, it helped quite a bit but still wasn't what I was after. So I wound up using some Neon Orange, here are the results, sorry about the photo quality.
Go to Walgreens® and buy "SINFUL COLORS" nail polish. All of my revolvers are painted with #53 "Summer Peach" on the front sight; and #56 "Neon Melon" on the rear sights. After you degrease the sights; paint them with "White Out" first, after dry then apply two coats of polish. The gun(s) will look like this..........
The neon colors are great, but I'm a fan of white fingernail polish on the front sight post. Both were done with el-cheapo dollar-store white fingernail polish. (one bottle does MANY revolvers) First I remove anything from the front sight post. (degrease it, defunk it, decosmoline it, etc) I tape it off with painters tape. I put 3-4 coats of the white, right near the top- one coat at a time, let dry, another coat, let dry, etc. It doesn't look PERFECT, up close, however, it is very very effective.
Here are two examples. First a S&W 442:
Next a Taurus 327: