Here is a litter with a group of agouti babies. The top one is a chinchilla, the middle one is a chestnut, the other is a lilac pearl.
Here is a chocolate and a lilac side by side. These two rabbits both carry the chocolate genetics but the lilac rabbit carries a dilute gene that allows the chocolate colour to be expressed as lilac. A blue rabbit is a black rabbit genetically that carries the dilute gene that allows the black colouring to be expressed as blue. Black, Blue, Chocolate and Lilac are all self colours -- their underbelly is the same colour as their back.