To display the colors like in the demo. First of all create attributes for that product from the Edit Product Page >> Select Variable Product then add Attributes and then create it’s variations.
Screenshot: https://jmp.sh/F6tGEcZ
After that navigate to Theme Settings > Shop > Attribute swatches > Grid swatch attribute to display >> Select Color.
Screenshot: https://jmp.sh/Sgq0UeR
Actually, you have not set the product as a Variable products. You have created the Simple Products and you are trying to apply/set attributes to the simple product. You should create the Variable products as shown in screenshot: http://prnt.sc/p289tv