彩虹色
[ #d60808, #d68308, #acd608, #31d608, #08d65a, #08d6d6, #085ad6, #3108d6, #ac08d6, #d60883 ]
彩虹渐变背景色
div::before {background: radial-gradient( #d60808, #d68308, #acd608, #31d608, #08d65a, #08d6d6, #085ad6, #3108d6, #ac08d6, #d60883 );opacity: 0.25;
}