By default, Odoo can not handle variant price extra with attributes, which are interdependent.
As far as I understand, you want to set the addon price for the attribute "Can" like this:
- Can at 1kg, price extra = 0
- Can at 4kg, price extra = +650
- Can at 20kg, price extra = +3400
In a second step you would like to define an extra price per kg of 120 for particular colors. As an example, the end price of Rooftop 101 20kg Color green shoud be 200 (base price) + 7000 (combined extra price) = 7200. This does not work.
Solutions:
1. Define a product template for each can unit (1kg, 4kg, 20kg) with only color attribute as variants. This is the easiest and recommended way, as it is also much more understandable and conceivable by your customers.
2. Do your own customization or check the App store for such a feature, for example this OCA module: https://apps.odoo.com/apps/modules/12.0/product_variant_sale_price/