Purchasing of chosen type of the product

I’m working on online-shop. I have two types of the one product which differ just in color. After the User chose one of the variants he precedes to payment.
How my web-site should understand which exactly type of the product (color) the Users wants to purchase?

I do not have a code right now. Just seeking for general advise what to start learning from? What is a general approach?

As I see it right now: there should be a selector. When User choose the variant the code determines which exactly product is it. I am a beginner, so understand that my explanation could be not clear

Thank you in advance!