How do I add the "Linear Color Cycle Animation" to just the border of my button instead of the whole background?

Site URL: https://k2.life

Here is my code. How do I make it so that only the border of the button changes color?

#block-yui_3_17_2_1_1594008918761_24680 {
  .sqs-block-button-element--medium {
    -webkit-animation: color rotate 25s
      linear infinite alternate;
    animation: color-rotate 25s linear
      infinite alternate;
  }
}
#block-yui_3_17_2_1_1594008918761_24680 {
  @-webkite-keyframes color-rotate {
  0% {background: #81c2ee}
  50% {background: #aea7f8}
  100% {background: #aea7f8}
}
}

Also changing the "background" to "{border: solid 1.75px #81c2ee}" did not seem to do the trick..

Hi. Have you solved it yet?