background-image: linear-gradient(red, yellow, blue, green); 
background-image: linear-gradient(rgba(255, 0, 0, .2), yellow, blue, green);

/*
    控制顏色漸變的方向
    to right -- 從左向右
    to top -- 從下到上
    to left -- 從右到左
    to bottom --- 從上到下（默認(rèn)值）
*/
background-image: linear-gradient(to right, red, yellow, blue, green);
background-image: linear-gradient(to top, red, yellow, blue, green);
background-image: linear-gradient(to left, red, yellow, blue, green);
background-image: linear-gradient(to bottom, red, yellow, blue, green);

/*0deg = to top -- 從下到上*/
background-image: linear-gradient(0deg, red, yellow, blue, green);
/*基于0度順時針旋轉(zhuǎn)45deg*/
background-image: linear-gradient(45deg, red, yellow, blue, green);
/*基于0度逆時針旋轉(zhuǎn)45deg*/
background-image: linear-gradient(-45deg, red, yellow, blue, green);

/*設(shè)置過渡顏色的起始位置*/
/*從過渡起始位置50px開始讓紅色和黃色之間產(chǎn)生顏色漸變效果*/
background-image: linear-gradient(to right, red 50px, yellow, blue, green);
background-image: linear-gradient(to right, red 50px, yellow 50px, blue, green);
background-image: linear-gradient(to right, red 50px, yellow 50px, yellow 100px, blue, green);

background-image: linear-gradient(to right
, red 0
, red 50px
, yellow 50px
, yellow 100px
, red 100px
, red 150px
, yellow 150px
, yellow 200px);
/**與上面重復(fù)寫漸變有相同的效果*/
background-image: repeating-linear-gradient(
        to right
        , red 0
        , red 50px
        , yellow 50px
        , yellow 100px
);