背景

• 三色背景（不渐变）

.columns-bg {
  background-image:
    linear-gradient(
      to right,
      #fffdc2,
      #fffdc2 15%,
      #d7f0a2 15%,
      #d7f0a2 85%,
      #fffdc2 85%
    );
}

工具

• Ultimate CSS Gradient Generator (opens new window)
• gradcolor (opens new window)
• cssmatic (opens new window)

参考资料

• CSS Gradients:css-tricks.com (opens new window)