We advise reading and familiarizing yourself with the Shopify Variants. It is an extremely well written and easy to understand.

There are different style to display product swatches

• Color Swatches
• Variant Images
• Simple Dropdown Style

Go to : Store Admin –> Products –> Add Product –> 

 Enter product title, add product images, add product tags, other details.

Now scroll down to Variants box and click on Add Variant

When you select Color Swatch style to display product swatches and products have 2 color to display as product swatch then add color images from Custom Color Sections.

Go to : Store Admin –> Customize –> Sections –> Custom Colors -> Add Color

Color name and Variant name must be same