[Theme: Yoko] white background on pages

Hi,
I am new to wordpress, 1st time ever even looking at code and I cannot seem to figure out how to change the white background of this theme. I have noticed this was asked before but I couldn’t figure out what I am doing wrong. I would simply like to go from white to deep purple color. Do I have to change it in several locations? If anyone could give me step by step process of all changes I would have to make I would appreciate it. I’m clueless, sorry ??

https://www.ads-software.com/extend/themes/yoko/