If you have color filter set for
Filterable (with results) there are only filters that contain any product. This is one possible reason for attribute's option to nit be displayed in layered navigation.
But for black option this is not a point there. Both products have black in their option, so filtering by black color doesn't matter, because in list there will be still two products. Notice, that blue an orange are only for one product - so if you choose one of these option form layered navigation you will see changes in collection.
So logic is - if filter doesn't change collection it won't be displayed.
To see it clearly, try uncheck black color for one of your products.