1) To begin you make such simple heads with only circles :

Use the grid (--> 5) to draw and to place easily your circles :

2) Move the different points to make some simple heads first :

3) You easily can change the colors :

4) With the option "draw --> split curves (--> 2)" you can move the new points to make more complex heads :

If someone wants the basic moho file I can send it on my server...
Hope you enjoy it...