how can I add a custom color for a variant color swatches for example 'mustard' ?

[frankcastle1042]

i'm using this theme https://dt-koka.myshopify.com/ and i want to add a custom variant pill color for example "mustard". how can I do this in code, without adding any app from the shopify app store? 

[frankcastle1042]

i dont have any file name "product.liquid" 😕 I also looked in the files have a similar name and I didn't find anything. 
I want the custom color swatches to be seen in the product page of any product and also for example in the home page when i use a section that shows some products with the differents color variants (from there is the picture of my first post)

[frankcastle1042]

i send you a message with the code.