You need to add an array of Options to the Product first:
{ "product": { "body_html": "uyt", "title": "gdf", "vendor": "my vendor", "product_type": "Stam4", "id": "407311507", "published": "false", "options": " [ { "name": "Size", "name": "Color" } ]", "variants": [ { "option1": "Small", "option2": "yellow", "price": 55, "inventory_quantity": 100 }