does vinylux damage your nails?

My nails are thin and soft and I've used all kinds of polish including gel and they are all harsh. I haven't had that problem with Vinylux. Keep in mind that you should always give your nails a break. P.S. This is the best home polish I have ever used and really lasts.

which color is a darker shade- #132 Negligee and #142 Romantique?

#132 Negligee has a blue shimmer which #142 Romantique does not. If your skin tone is on the warmer side, #132 Negligee may NOT be the way to go. I am cool toned and use one coat of #132 Negligee with a strip of #151 Studio White (semi-sheer) and a clear gloss top coat. and For me, it is the perfect French with a little something extra.

can this color be used in a french manicure?

Yes..I pair this color with the vinylux color in cream puff and the manicure is GORGEOUS!!!!!

Is this the color that has a little bit of purple sheen to it?

No, I wouldn't say it has a purple sheen to it. But it is very sheer. The CND website says it is semi-sheer, but I would say it is sheer. Takes me three coats to get a nice even color. But with all that said, it is still my favorite vinylix color.