Try to add the following code snippet to the Custom CSS area in Theme Settings
.product-image-summary-wrap .swatches-select .colored-swatch:after,
.product-image-summary-wrap .swatches-select .image-swatch:after {
content:none;
}
.product-image-summary-wrap .swatches-select .colored-swatch,
.product-image-summary-wrap .swatches-select .image-swatch {
box-shadow: 0 0 0 2px #dadada;
border: 4px solid white!important;
-webkit-transition: all .25s ease;
transition: all .25s ease;
}
.product-image-summary-wrap .swatches-select .colored-swatch.active-swatch,
.product-image-summary-wrap .swatches-select .image-swatch.active-swatch,
.product-image-summary-wrap .swatches-select .colored-swatch:hover,
.product-image-summary-wrap .swatches-select .image-swatch:hover {
box-shadow: 0 0 0px 2px black;
}