flaskdashboard/app/base/static/assets/scss/black-dashboard/custom/_alerts.scss

.alert{
    border: 0;
    color: $white;

    .alert-link{
      color: $white;
    }

    &.alert-success{
      background-color: darken($success, 10%);
    }

    i.fa,
    i.tim-icons{
        font-size: $font-paragraph;
    }

    .close{
        color: $white;
        opacity: .9;
        text-shadow: none;
        line-height: 0;
        outline: 0;
    }

    span[data-notify="icon"]{
      font-size: 22px;
      display: block;
      left: 19px;
      position: absolute;
      top: 50%;
      margin-top: -11px;
    }

    button.close{
      position: absolute;
      right: 15px;
      top: 50%;
      margin-top: -13px;
      width: 25px;
      height: 25px;
      padding: 3px;
    }

    .close ~ span{
        display: block;
        max-width: 89%;
    }

    &.alert-with-icon{
        padding-left: 65px;
    }
}

.alert-dismissible {
    .close {
        top: 50%;
        right: $alert-padding-x;
        padding: 0;
        transform: translateY(-50%);
        color: rgba($white, .6);
        opacity: 1;

        &:hover,
        &:focus {
            color: rgba($white, .9);
            opacity: 1 !important;
        }

        @include media-breakpoint-down(xs) {
            top: 1rem;
            right: .5rem;
        }

        &>span:not(.sr-only) {
            font-size: 1.5rem;
            background-color: transparent;
            color: rgba($white, .6);
        }

        &:hover,
        &:focus {
            &>span:not(.sr-only) {
                background-color: transparent;
                color: rgba($white, .9);
            }
        }
    }
}