Group same products and show one on collection page

[Julia_2]

Hi all,

I am quite new on Shopify - so I need your help.

I have some products that have different colors. The problem is that every color has a unique product.id 

I would like to group these products together and show only one on the product page with available colors.
Now I'm using this app https://apps.shopify.com/product-colors (it groups products and show available colors on the Product page.) 

But how to show only one product  of the group?

Thank you!