Cream butter, sugar, and vanilla until light and fluffy
Add 1 egg at a time, mixing well between addition
Add lemon zest and juice then mix well to combine
Mix in the flour 1/3 at a time, mixing well between additions
Split mix into 4 batches, adding a colour to each separate batch. Try just a couple of drops at time a until you get a bright colour.
Refrigerate for 2 hours
Roll dough into small balls, roll in icing sugar, place on a non-stick cookie tray
Bake at 175°c for 10-12 minutes