You cannot make those changes directly in the MC GUI (if that if that is what you are looking for). These colors are different for each skin, and you have to edit the desired skin's
main.xml file to modify background colors (via changing hex color codes in several locations).
As for designating rows 1 -15 to use one alternating pair of colors, and then subsequent row "sets" use different alternating pair of colors? No - not possible. You would have to put in a feature request, but I find it highly doubtful something like that would ever be implemented. As someone who has created skins, I personally would not welcome having to design for that, and
every current MC skin would have to be updated to accommodate such a change if it were implemented.
I suggest reading the first post here
https://yabb.jriver.com/interact/index.php/topic,128460.0.html. If after reading that you still want to pursue changing the background colors for a specific skin, then download the
Dream-in-Blue skin. Not to use that skin, but simply to get the
main+comments.xml that is included in the download. With the instructions/notes found in the
main+comments.xml as reference, open the
main.xml file for the skin you want to modify and change the background hex codes to your preferred color(s). Off the top of my head, you will need to make edits in the LIST and VIEW HEADER sections, but there may be additional sections I'm forgetting.
Also... if you are editing a skin that comes with MC by default (Modern Cards, Noire, Aruba, Green Eyes, Thunderstorm, among others), be sure to change the skin name
in the XML file itself - otherwise, anytime MC updates it will overwrite your edits. This is explained further in the
main+comments.xml. Good luck!