Problem using woocommerce and color swatch

I have a website where I am importing products from various other websites. I am using WooCommerce Variation Swatches for variable products color swatches. I don’t know why some of the products shows the registered colors in the drop-down inside Attributes tab – https://drive.google.com/open?id=1nJ5kluN4A8iuIrJuJeDZK9EdRePKZeR5. However, some of the products shows textarea instead of select dropdown for the color options – https://drive.google.com/open?id=1cQTSregl5OVJahPws7Xnc-G8X1Y7WtYX.

I guess this is the reason why color dropdown is displayed instead of swatches in the single product page (the products having textarea for colors in the backend) – https://drive.google.com/open?id=1reDDaqthvgWH9qPIth6CB1GX3F2CoPef. I want to display swatches instead of drop-down in the single product page. I am new WooCommerce user.

Any help would be more than appreciable.