So, i've created a triangle that points up with a background color of#222 using pure CSS. I want to add a red 1px border to that triangle, but I have no idea how.
.arrow-tip {
    width: 0; height: 0; 
    border-left: 15px solid transparent;
    border-right: 15px solid transparent;
    border-bottom: 15px solid #222;
}
 
     
    