best linear-gradient color for border code example

Example 1: linear gradient border

div-border-and-content-background {
  border-top: double 5px transparent;
  
  /* first gradient is for card background, second for border background */
  background-image: linear-gradient(white,white), linear-gradient(to right, grey, black);
  background-clip: padding-box, border-box;
  background-origin: border-box;
  }

Example 2: css border top linear gradient

.bordertest {
    height:300px;
    width:300px;
    border-top:30px solid #c4268c;
    background:#000;
    position:relative;
    margin:1em;
}
.bordertest:first-child:before {
    content:'';
    position:absolute;
    width:100%;
    height:30px;
    background:linear-gradient(to left, #c4268c, #9a0b72);
    top:-30px;
    left:0;
}