смена цвета картинок при наведении с серого на цветной. используется 1 картинка, css, thumbnail

.py

from sorl.thumbnail import get_thumbnail
partners = []
total_width = 0
for partner in PartnerItem.objects.filter(published=True).order_by('?'):
    im = partner.get_first_picture()
    tmp = get_thumbnail(im.image, 'x64', crop='center center')
    total_width += tmp.width
    if total_width > 960:
        break
    else:
        gray = get_thumbnail(im.image, 'x64', crop='center center', colorspace='GRAY')
        partners.append({
            'title': partner.title,
            'link':  partner.link,
            'im_gray': gray,
            'im_colored': tmp,
            })

css

.partner_link:hover .partner_gray {
    display: none;
}
.partner_link:hover .partner_color {
    display: block;
}
.partner_gray {

}
.partner_color {
    display: none;
}

html

{% for partner in partners %}
    <div class="item">
        <div class="gray-block">
            <a class="partner_link" href="{{ partner.link }}">
                <img class='partner_gray' src="{{ partner.im_gray.url }}" width='{{ partner.im_gray.width }}' height="{{ partner.im_gray.height }}" alt="{{ partner.title }}"/>
                <img class='partner_color' src="{{ partner.im_colored.url }}" width='{{ partner.im_colored.width }}' height="{{ partner.im_colored.height }}" alt="{{ partner.title }}"/>
            </a>
        </div>
    </div>
{% endfor %}