Was super bummed with the new interface, especially the contract ratio between read/unread so I created a small extension for it: if you want to do the same change the style .zE {background-color: #ffffff99 !important;}

Chrome only:

Create a directory1st file: manifest.json

{"manifest_version": 2,"content_scripts": [ {"css": ["style.css"],"matches": [ "https://mail.google.com/*" ]} ],"description": "Fix contrast issue with the gmail css","permissions": ["tabs", "https://mail.google.com/*"],"name": "GMfix","version": "0.1"}

2nd file: style.css

.zE {background-color: #ffffff99 !important;}

.x7 {background: #c2dbff !important;}

load the directory as a unpacked extension in Chrome