Convert a Template to a Website

I'm looking for some customization on a BigCommerce template and I was wondering if you could help and what costs would be involved. We want to create two categories with a different background colour in each. The First category we want a background colour of #BFBAB3 The Second category we want a background colour of #D3E1E6 We are using the BigCommerce template “Classic Next (light)” I was chatting to their support people and it seems the background colour is a global command. He said we need to create a line of code in [login to view URL] that will load a colour when the category is visited. Do you have a template that has this functionality or can you help create it for this BigCommerce template? I'm not tied into using this template but whatever template we use will need to be responsive, that is will adjust well to different screen sizes, tablets, phones etc. The menu system will need to be able to display the category / a sub category / and a sub category of that. I hope this all makes sense to you. If not contact me and I'll try to clarify it. Looking forward to your response