CSS - can we add different colors as borders for an svg polygon?

Question

HTML

<svg class="triangle">
    <polygon  class="my_polygon" style="" points="9 0, 0 9, 9 18" fill="#FFFFF"/>
  </svg>

CSS

.my_polygon {
 width: 20vw;
  height: 20vw;
  position: relative;
  left: 0;
  top: 0;
  stroke: red;
  fill: red;
  border: 1px solid red;
}

This gives us something like this :

Now if I wish to change the border color (in our case stroke) of only one side of the triangle say , is there a way to do that ?