That theme is called alphablue, you can find it in the Play Store but it's not free, but I think you can download it for free on the XDA thread.
I use WinRAR to mod my roms without unsigning the zip file and I use Notepad++ or Wordpad to change the values of certain scripts and files. There are also other tools I used to apply various useful patches such as Ultimate Jar Tool to supercharge the services.jar. and there's tools that will re-odex or deodex roms for you.
The possibilities are endless, it all depends on how much you know about something, don't ever try something you don't understand because it could end up being harmful for your device, unless you take the time to learn about it, nobody wants a bricked phone at the end of the day and believe me I've already fully bricked this device and brought it back to life a few times so technically my phone is a zombie lol
Doing research goes a long way, I can no longer look at myself as a noob anymore after learning everything I know about Android.