JMS Colors for Virtuemart allows you to create colors for each product, each color will has own price and images. Colors and prices also will update to cart, order, invoice.
http://www.joommasters.com/index.php/joomla/joomla-plugins?view=document&doc_id=20
Demo link:
http://demo25.joommasters.com/index.php?option=com_virtuemart&view=productdetails&virtuemart_product_id=17&virtuemart_category_id=6 (http://demo25.joommasters.com/index.php?option=com_virtuemart&view=productdetails&virtuemart_product_id=17&virtuemart_category_id=6)