When you're selling your house, you definitely want to use neutral and lighter colors. This is especially important if you have rooms with very taste specific or polarizing colors, as well as if you have dark color and many color in different rooms. If you paint with a neutral and consistent color, it will appeal to more buyers and it will make your space look larger.
Now, neutral doesn't necessarily mean white. In fact, white is not your best choice as it often looks sterile and too neutral. It drains the personality of your home. Linen white used to be used, but for most buyers this is also a big turn off...as a) it shouts builder grade and b) it's too yellow and yellow is dated. Instead go for a light cooler tone.
Based on what new home buyers are actually painting their homes with, a light gray is currently the most popular...and buy far. We often recommend and use Sherwin Williams Silverpointe. This is an excellent choice as it's neutral (and a neutral gray). It's light enough to make your home look light and airy. It also contrasts well with white base molding and other trim. There are other gray options that also work well.
When you're getting ready to sell your Long Island home, consider using a light neutral gray. It will help your home show better and is the most popular among new home buyers.
Oh, and trim should always be white. If your trim is another color, paint it now. Colored trim or trim that is the same color as the base molding is a huge turn off. And, it just looks cheap.