metamask-extension/ui/components/component-library/button-link/button-link.scss

.mm-button-link {
  color: var(--color-primary-default);
  background-color: transparent;

  &:hover {
    color: var(--color-primary-default);
    opacity: 0.5;
  }

  &:active {
    color: var(--color-primary-default);
    opacity: 0.5;
  }

  &.mm-button--disabled {
    &:hover {
      color: var(--color-primary-default);
      opacity: 0.3;
    }

    &:active {
      opacity: 0.3;
    }
  }

  &--type-danger {
    color: var(--color-error-default);

    &:hover {
      color: var(--color-error-default);
      opacity: 0.5;
    }

    &:active {
      color: var(--color-error-default);
      opacity: 0.5;
    }

    &.mm-button--disabled:hover {
      color: var(--color-error-default);
    }
  }
}