@ehmjay : please attached the version with the icon you requested.
I made another version with white font (instead of blue) when black background selected, and a new icon for news message (not ehmjay's).
As requested, here is a (very) little "how to".
How to change background, icon, pictures ?
=> just open the apk with 7zip
and drag the requested icon, background, pictures you want to modify.
This is very easy.
How to change the font color ?
You need an apk tool for that. I use Apk Manager but this app is no longer avalaible.
So you may use Apk Multitool
, which is the new name of Apk Manager.
First, you have to copy your apk in the directory "place-apk-here-for-modding" of ApkMultiTool.
Then, launch ApkMultiTool, set the current project (option 23), decompile the apk (option 9), go to the directory "projects\Mms.apk\res\values\" of the ApkMultiTool directory and open with notepad the file "colors.xml".
It's here you can modify the color of the font. Colors are coded in hexa code (see here
Save and close the file.
Now, you have to compile the apk (option 11), say no to the question "Is this a system apk". Say no to the next question too.
In the directory "place-apk-here-for-modding", there's a new file "unsignedMms.apk". Open 7zip in two panels mode, in the first panel, open "unsignedMms.apk", in the second panel, open a copy of mms.apk.
Then, copy the file "resources.arsc" of the "unsignedMms.apk" to the mms.apk.
Closes files, push your mms.apk in your phone dir (system/app) and enjoy...
How to change anything else ?
Hum, I'm not a dev, I haven't an answer for this question.