It's in each individual apk's files
res/values and open the colors.xml
The other option is to find the individual xml for each thing you want to alter, and change the color there.
In the framework-res.apk (using that, since it's the only one i have decompiled, at the moment, and I'm lazy)
In res/drawable/app_icon_background.xml, you will see the following
<?xml version="1.0" encoding="utf-8"?>
<item android:state_selected="true" android:drawable="@drawable/icon_highlight_square" />
<item android:drawable="@color/transparent" />
Where you see <item android:drawable="@color/transparent" />
that references the color.xml... Now you could change it in color.xml, and have everything that says 'transparent' be changed as well, or you could change @color/transparent to something like @color/#ffffffff and have that individual xml call for the color white...
but @color/#ffffffff above should look like
transparency of color=ff,80,00
hexcolorcode=ffffff (white etc.)
you can add colors to colors.xml and point apk colors there too