Not sure why the page is structure like this, but the slider is embedded within HTML pre tags. pre tags are usually used to to display code; the pre stands for pre-formatted text, which tells the browser to leave the line breaks alone (i.e., don’t join the lines). The reason for the alternate colors is that it is easier to read lines of code when the lines are more distinct from one another.
You can get rid of the gray stripes by adding this CSS rule to either the theme’s Custom CSS option (if it has one), via a child theme, or by using a CSS plugin like JetPack or Custom CSS Manager:
#Content pre {
background: transparent;
}
You can also edit the home page to take the slider out from within the pre tags.