Yes, it can be done. Please share your website URL.
I just checked your website main page is black, right?
So you need other pages background white?
For other pages will have to write code accordingly and customize it for the following:
1) Background color
2) text and font colors
3) Maybe icon colors
4) section background and text colors
5) All pages footer colors and text colors
6) Header background color and text colors.
This is the customization work. I thought it's just a background color need to change but there are many things that will have to do if change with other pages.
As this is purchased theme so will have to make customizations accordingly.
Let me know your thoughts. We can discuss further.
You purchased theme and you paid for your custom changes then they have to give proper services for this.