I think the important thing is to go with your coloring. It can make your hands look really sickly and pale if you use the wrong color, esp. one that's too saturated (i.e. "colorful" on a scale from total color to grayish color). Plus, I think really long nails on women look very unattractive - I always think of first, the grunge that collects under there, and second, all the crap I would have to do for
her since she has essentially rendered herself impaired. And aesthetically, they just look tacky.
You're correct about skin tones. Darker reds look far better on my hands. I have seen women who look great with pastel colors on their nails. When talking about long nails, I suppose you mean the kind one applies, not one's real nails. But I agree, this can be fairly frightening. The test for me is when typing becomes impaired.