Disney look: "Neutral shades." They pretty much mean pale to light pink, beige, tan, and light, light browns, however depending on your skintone, this might change. A light pink on me is barely noticeable, but on my very tan friend, it looks brighter. French manicure is acceptable, as long as it's the traditional pink/neutral and white. Your nail can't be longer than 1/4 inch longer than your fingertip. Yes, there are managers who will whip out a ruler and measure.
I'm the queen of blue/green/teal/neon nails, but while I worked at WDW, I rarely had polish on my fingernails. If I did, it was light pink or a beige shade. HOWEVER... my toenails were often neon orange, highlighter-yellow, or aqua blue, as they were hidden by my work shoes at all times.