How to set styles for checkboxes in Symfony2?

I have problem with checkboxes which I render by FormBuilder.

The problem is that <input/> is generated inside <label></label>. The result is the following:

I don't know what I should do to format this checkboxes to the state on the right side of the image. I check documentation and I have not found any methods which can give access to change the way how this fields are rendered.

Twig:

{{ form_widget(form.colors, { 'attr': {'class': 'MY-CLASS'} } ) }}

HTML Result:

<div id="template_colors" class="MY-CLASS">
    <input type="checkbox" id="template_colors_0" name="template[colors][]" value="white">
    <label for="template_colors_0">White</label>

    <input type="checkbox" id="template_colors_1" name="template[colors][]" value="red">
    <label for="template_colors_1">Red</label>

    <input type="checkbox" id="template_colors_2" name="template[colors][]" value="black">
    <label for="template_colors_2">Black</label>
</div>