Freshen up your yellowing nail tips before a manicure by soaking your fingernails in a bowl filled with lemon juice. Let your nails sit for a few minutes, then buff the tops of your nails, removing the yellow tone and prepping your acrylics for a new manicure.
Use a base coat before any manicure. If your nail technician doesn't already use one, ask her to do so. Slipping a base coat on your nails before applying color can keep your acrylics from becoming discolored by protecting the nail from the paint.
Seal in your color. Always use, or ask for, a UV coating on top of your French manicure. Applying a layer of clear polish designed to protect your manicure from the sun can help protect your newly painted fingers from fading and discoloration.
Stamp out that cigarette and kick the habit as soon as possible. Holding a smoldering ciggie between your fingers can cause your French tips to turn yellow in a hurry. Your manicure and your body will thank you.
Ask your nail stylist what's up with your nails. If your acrylic tips turn yellow or gray after a manicure, it could be a sign that your nail technician used dirty or improperly mixed products. It also could be a sign that your acrylics are cracked or not glued down properly. Go back to the salon where you got your tips and give them a chance to fix the problem. If your nails continue to show discoloring, consider switching salons.