Most of a shop’s complexity is not on screen. It is in the rules: what a parcel costs to the other side of the country compared with next door, what happens when a size runs out, how VAT is shown on the invoice. I would rather spend the first week on those rules than on colours.
The aim is a shop you can run on a quiet Monday morning without calling me: you see the orders, print the labels, update the stock, and customers get clear emails at each step.

