i3 gaps is a fork from i3 and it provides the same functionality but with more options to define the gaps between the different applications.

There are some settings that are interesting to know. You can always read from the source here.

We will also change the colours of the borders around our applications if we set the borders in i3 gaps.

This is the code coming from i3 guide documentation.

# class                 border  backgr. text    indicator child_border
client.focused          #4c7899 #285577 #ffffff #2e9ef4   #285577
client.focused_inactive #333333 #5f676a #ffffff #484e50   #5f676a
client.unfocused        #333333 #222222 #888888 #292d2e   #222222
client.urgent           #2f343a #900000 #ffffff #900000   #900000
client.placeholder      #000000 #0c0c0c #ffffff #000000   #0c0c0c

client.background       #ffffff

Colouring is changed in this picture to red and blue. Screenshot from the tutorial underneath.

borders-colouring-i3

 

The code is being copied from this source.