如何用css画三角形

1、
#triangle02{
    width: 0;
    height: 0;
    border-top: 50px solid blue;
    border-right: 50px solid red;
    border-bottom: 50px solid green;
    border-left: 50px solid yellow;
 }

2、

#triangle03{
    width: 0;
    height: 0;
    border: 50px solid transparent;
    border-top: 50px solid blue;
    }
#triangle04{
    width: 0;
    height: 0;
    border: 50px solid transparent;
    border-right: 50px solid red;
    }
#triangle05{
    width: 0;
    height: 0;
    border: 50px solid transparent;
    border-bottom: 50px solid green;
    }
#triangle06{
    width: 0;
    height: 0;
    border: 50px solid transparent;
    border-left: 50px solid yellow;
    }