How to remove the vertical margins/padding from a particular section or page

Site URL: http://https/fullcirclemicrobes.com/problem-solution-1

For each new page or section I create within my site index, there's a built-in padding or margin at the top and bottom that runs the width of the screen. I've looked at a few similar questions and tutorials on YT but haven't been able to make those CSS fixes work for me. In this particular example, I want to eliminate the grey areas above and below my text blocks so that the section/page will be divided in half vertically with the left side all grey and the right side all green.

Add to Home > Design > Custom CSS

.Index-page-content {
	padding-top: 5px;
	padding-bottom: 5px;
}