This is the same version ecsnead posted but I edited a few things to make the "read message" background a little bit different than the unread... there are 2 versions.. one has a gray tone (#151515) and the other has a very dark gray tone (#080808).. The first one is very easy to see the difference but I like the second one because on the screen shot ya can't see much of a difference but if ya just tilt the phone a little, you can see the difference very clearly so this version doesn't take away from the 'Blacked Out' that ecsnead and I were going for... I made both versions as update.zips and the dark gray one as a signed apk.. however, we've tried our best with our inverted apps to recreate issues that some users are facing and through this, we've found that Gmail likes to be in system/app just as our inverted markets do.. you might be fine installing to data (some roms have it there as default anyway) but if you use the apk install and you get force closes, just use root explorer and move the com.google.android.gm (-1 , or -2) over to system/app and rename it Gmail.apk.. then reboot.. works great then.. we're not sure why some users have no issues while others do but ecsnead69, Mbk and myself have tested numerous avenues with these issues and are trying our best to offer top knotch inverted/Blacked Out/Dark apps that any and all users can install... so if you have issues, please post them so we can assist you.. don't complain or nag that something "should be" different.. we put hours and hours into what we do and we've usually tried 20+ possibilities and the one's we post are the one's we're most proud of and they meet a happy medium that anyone wanting an inverted version will be totally blown away by... as always, make a back up or have one ready before modding your phone/device since we aren't responsible for you or your device... our other version has around 1600+ downloads in a couple days so thanks to everyone supporting us and using our/his/or my inverted apps.. Enjoy!.. 
DOWNLOAD LINKS:
1. http://bit.ly/DarkGmailGrayReadBG Lighter gray background for read messages - Update.zip so flash in recovery
2. http://bit.ly/DarkGmailDarkGrayReadBG Dark Gray background for read messages - Update.zip so flash in recovery
3. http://bit.ly/signedGmailBlackedOutDarkGrayReadBG Signed apk install.. make sure you uninstall Gmail from system, reboot, install this one.. if it fc's, move it to system/app, rename it Gmail.apk, reboot...
DOWNLOAD LINKS:
1. http://bit.ly/DarkGmailGrayReadBG Lighter gray background for read messages - Update.zip so flash in recovery
2. http://bit.ly/DarkGmailDarkGrayReadBG Dark Gray background for read messages - Update.zip so flash in recovery
3. http://bit.ly/signedGmailBlackedOutDarkGrayReadBG Signed apk install.. make sure you uninstall Gmail from system, reboot, install this one.. if it fc's, move it to system/app, rename it Gmail.apk, reboot...