Additional note to my previous reply:
You have to make sure your original logo graphic is small enough so the “Skip Cropping” button will appear as an option when uploading.
Thank you @heyjk for the code! I wondered what those boxes meant! Now I have the arrows. 😀
I had this problem and discovered that when I skipped cropping after selecting it, my logo remained clear. 😀
Ok, after all that searching, I found the answer:
The menu background color for mobile and tablet view conforms to the Main Body primary color.
So, in case anyone else needs help with that…. there ya go!