// так работает как надо
return array(
    'product/<category:\d+>/<item:\d+>/<color:\d+>/<size:[A-Za-z-0-9\s]+>.html' => 'product/item/view', // product/20/11/3/XL.html
    'product/<category:\d+>/<item:\d+>/<color:\d+>.html' => 'product/item/view', // product/20/11/3.html
    'product/<category:\d+>/<item:\d+>.html' => 'product/item/view' // product/20/11.html
);

// не тк как надо, если прописаны по длине
return array(
    'product/<category:\d+>/<item:\d+>.html' => 'product/item/view' // product/20/11.html
    'product/<category:\d+>/<item:\d+>/<color:\d+>.html' => 'product/item/view', // product/20/11?color=3
    'product/<category:\d+>/<item:\d+>/<color:\d+>/<size:[A-Za-z-0-9\s]+>.html' => 'product/item/view', // product/20/11?color=3&size=XL
);