Darker colors, including jewel tones and some earthy colors, are popular for fall and winter sweaters. For spring and summer sweaters, on the other hand, stick to lighter colors. White, pastels, and lighter earth tones are popular choices. With that said, classic neutral colors can be worn in any season if they’re styled right. A black button-down cardigan, for example, can be worn in the summertime with black strappy sandals or a pastel dress featuring black flowers.