Answers for "2 color border css"

border color css

border: 1px solid #000000;

border color css

border: 1px;
border-color: #3581fc;

double border color css

.double-border {
  display: block;
  clear: both;
  background: red;
  border: 5px solid yellow;
  outline: 5px solid blue;
  transition: 0.7s all ease-in;
  height: 50px;
  width: 50px;
}
.double-border:hover {
  background: yellow;
  outline-color: red;
  border-color: blue;
}
<div class="double-border"></div>

border-color

div {border-color: coral;}