background and content appearing as different 'whites'

Hi there,

this CSS you have is adding a box shadow to the article:

.inside-article,
.sidebar .widget,
.comments-area {
	box-shadow: 0 0 60px rgba(0,0,0,0.05);
}

It's that which is creating an 'optical illusion' that the two colors are different.

Thanks David, but do I find and change this CSS?

Thanks David, but how do I find and change this CSS?

Go to Customizer > Additional CSS and you will find it in there.

It only worked! thanks very much, much impressed.

Glad to be of help