By Marianne Mychaskiw
Updated Mar 17, 2014 @ 9:00 am
Molly Sims Red Hair
Credit: WireImage; BEImages

Ever since Molly Sims swapped her trademark blonde for a warm auburn hue, we've been seeing red and have been tempted to make a similar shift in shade. Out of all the tones in the hair color spectrum, red tends to fade the fastest. Why? The dye contains a larger color molecule, meaning it slides out of the hair shaft much easier than its blonde or brunette counterparts.

Because of this, Sims now takes an extra step to preserve her color before lathering up. "My new favorite product is the Nexxus Color Assure Pre-Wash Primer ($19; It's the secret to preserving my color! ," Sims tells "I use it on my hair right before showering to keep water out, and it gives me two times longer color protection. It's kind of like when you prime a wall or use a primer as a way to make your makeup stay on longer."

In addition to taking preventative steps, be sure to trade your current shampoo and conditioner for color-preserving versions -- bonus points if they're formulated especially for red hair. We also recommend investing in a red hair gloss, or a color-depositing conditioner to keep your hue fresh between salon appointments.