/*Christoph*/

.validation-message {
    display: none;
    width: 100%;
    margin-top: 0.25rem;
    font-size: 80%;
    color: #dc3545;
}

.invalid ~ .validation-message {
    display: block;
}

.form-control.invalid {
    border-color: #dc3545;
    padding-right: calc(1.5em + 0.75rem);
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='none' stroke='%23dc3545' viewBox='0 0 12 12'%3e%3ccircle cx='6' cy='6' r='4.5'/%3e%3cpath stroke-linejoin='round' d='M5.8 3.6h.4L6 6.5z'/%3e%3ccircle cx='6' cy='8.2' r='.6' fill='%23dc3545' stroke='none'/%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right calc(0.375em + 0.1875rem) center;
    background-size: calc(0.75em + 0.375rem) calc(0.75em + 0.375rem);
}

    .form-control.invalid:focus {
        border-color: #dc3545;
        box-shadow: 0 0 0 0.2rem rgba(220, 53, 69, 0.25);
    }

textarea.form-control.invalid {
    padding-right: calc(1.5em + 0.75rem);
    background-position: top calc(0.375em + 0.1875rem) right calc(0.375em + 0.1875rem);
}

.form-check-input.invalid ~ .form-check-label {
    color: #dc3545;
}

.form-check-input.invalid ~ .validation-message {
    display: block;
}

.new-input {
    display: -ms-flexbox;
    display: flex;
    -ms-flex-align: center;
    align-items: center;
    /*padding: .375rem .75rem;*/
    padding: .375rem .75rem;
    margin-bottom: 0;
    font-size: 2rem;
    font-weight: 400;
    line-height: 0.7;
    color: #495057;
    text-align: center;
    white-space: nowrap;
    /* background-color: #e9ecef;*/
    background-color: #ffffff;
    /*  border: 1px solid #ced4da;*/
    border: 1px solid #ffffff;
    border-radius: .25rem
}


/* Chrome, Firefox, Opera, Safari 10.1+ */
.form-control::placeholder { 
    color: lightgray;
    opacity: 80;
    font-size: small;
}


<script >
$('#comment').keyup(function () {
  var characterCount = $(this).val().length,
  current = $('#current_comment'),
  maximum = $('#maximum_comment'),
  theCount = $('#the-count_comment');
  var maxlength = $(this).attr('maxlength');
  var changeColor = 0.75 * maxlength;
  current.text(characterCount);

  if (characterCount > changeColor && characterCount < maxlength) {
    current.css('color', '#FF4500');
    current.css('fontWeight', 'bold');
  }
  else if (characterCount >= maxlength) {
    current.css('color', '#B22222');
    current.css('fontWeight', 'bold');
  }
  else {
    var col = maximum.css('color');
    var fontW = maximum.css('fontWeight');
    current.css('color', col);
    current.css('fontWeight', fontW);
  }
});
</script >