Yes, it requires use of userChrome.css and this is documented more extensively in Thunderbird articles. Anyway, here is the code to place in that file:
#threadTree treechildren::-moz-tree-row(odd) {
-moz-appearance: none !important;
background-color: #ffff00 !important; }
For basics, in profile, create a folder named chrome. In that folder create a text file named userChrome.css and place the above text in it. The function should appear when you next start Postbox.
My sample color (yellow) is not advised, as it's just an example. Also, several Postbox themes show sender in bold. AND, userChrome.css is not supported, but it's harmless, so I anticipate no repercussions. I have many customizations there.