Why does it genereate so many pictures ?
Android Holo Colors Generator is based upon the default holo theme (in Android source code) which use as many pictures as there (and even more !). You may remove those you won't use and adjust the styles.xml to unreference those pictures. For example, if you never disable widgets, you can remove the "disabled" pictures. You can also remove density you don't want, for example mdpi. In that case, if a device with medium density use your application, hdpi pictures will be used. As you can see, we do not generate ldpi, to avoid many more pictures (see Why the low density (ldpi) is not generated ?).

Why the low density (ldpi) is not generated ?
Android Holo Colors Generator is based upon the default holo theme (in Android source code) which does not provide any picture for low density devices. Moreover, ldpi represents less than 2% of the Android Market Share. Finally, if a device is in ldpi, it will use the mdpi or hdpi pictures (more info).

My application crash on gingerbread or froyo when adding optical bounds (red borders).
Indeed, Google introduced a new PNG processor in gradle plugin 0.9.1 (see documentation). This PNG processor does not crunch the png as before, so that application crash at runtime (see this issue). The solution is to use the old png processor in your gradle build (when using 0.9.+) :
android.aaptOptions.useAaptPngCruncher = true
Thanks to Javier Silva for this solution.

Why the ProgressBar is not with my color ?
When using a ProgressBar, the default picture is the rolling ProgressBar. In order to get your pictures, set the following to your ProgresBar :
style="?android:attr/progressBarStyleHorizontal"

On Mac OS, when I copy the folders, it overwrite previous content
It is the default behavior of Finder. To avoid this, use another tool, for example muCommander or command line :
ditto origin_folder destination_folder

The generator does not provide action bar files, how to get them ?
There is another website for that. Go to actionbarstylegenerator to get your action bar pictures.

How to use TabWidget ?
You should have a look at google documentation for the basis. To use the custom color, replace the default indicator like this:
View tabIndicator = LayoutInflater.from(this).inflate(R.layout.tab_indicator_holo, mTabHost.getTabWidget(), false); TextView title = (TextView) tabIndicator.findViewById(android.R.id.title); title.setText("Tab 1");

How to help you to improve the generator ?
You can help with a donation :