I was looking for the
Resources tab in Chrome Developer Tools and couldn't find it until I saw there is a new tab that I didn't recognize named
Application, it looks like it is containing all the things that were in the old
Resourcestab but not colorful as before(now it's all gray).
What is the difference?
Why have they done this?
Why it's gray and not colorful?
Chrome have introduced new features as well as keeping all the previous ones from the Resources panel. The new features revolve around Progressive Web Apps, i.e. use of Service Workers. You can read Debug Progressive Web Apps for details on this. Some really useful stuff.
The Resources panel has been renamed to the Application panel. All of the features from the Resources panel are still available in the Application panel. See here