<select id="your_select">
  <option>Option 1</option>
  <option>Option 2</option>
  <option>Option 3</option>
  <option>Option 4</option>
  <option>Option 5</option>
  <option>Option 6</option>
  <option>Option 7</option>
  <option>Option 8</option>
  <option>Option 9</option>
</select>
<span id="slave" class="option0">option0</span>
​

$('#your_select').on('change', function() {
    var value = $('option:selected', this).text().replace(/Option\s/, '');
    $('#slave').removeClass().addClass('option' + value).text('option' + value)
});​

Working Demo 1

If you select is like following:

<select id="your_select">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
  <option value="option4">Option 4</option>
  <option value="option5">Option 5</option>
  <option value="option6">Option 6</option>
  <option value="option7">Option 7</option>
  <option value="option8">Option 8</option>
  <option value="option9">Option 9</option>
</select>
<span id="slave" class="option0">option0</span>

Then

$('#your_select').on('change', function() {
    var value = this.value;
    $('#slave').removeClass().addClass(value).text(value)
});​

Working Demo 2

HTML:

​<select id="master">
    <option>Content 1</option>
    <option>Content 2</option>
    <option>Content 3</option>
    <option>Content 4</option>
    <option>Content 5</option>
    <option>Content 6</option>
    <option>Content 7</option>
</select>
​<span id="slave">option0</span>​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

jQuery:

​$('#master').change(function() {
    var selected = $(this).val();
    $('#slave').removeClass().addClass('option' + selected);
});​​​

CSS:

​.option​0 {
    background-color: red;
}
.option1 {
    background-color: green;
}
.option2 {
    background-color: brown;
}
.option3 {
    background-color: yellow;
}
.option4 {
    background-color: blue;
}

...

See a live example here

Alternatively, if you want to have any content between the option tags, apply a custom attribute 'data-position' and use this jQuery:

$('#master').change(function() {
    var selected = $('#master option:selected').attr('data-position');
    alert(selected);
    $('#slave').removeClass().addClass('option' + selected);
});​

See an updated live example here