Quick answer
Many control cables identify each core by a printed number on uniformly coloured insulation, often black, rather than by a different colour for each core. The reason is practical. A cable with 12, 24 or 61 cores cannot be separated by colour alone, because only a limited number of colours can be told apart reliably on site, and a number printed on every core allows each one to be matched to a terminal in the panel schedule.
The exact scheme depends on the standard and the manufacturer, so the core identification method should be confirmed on the datasheet before ordering. APAR's LV XLPE/PVC control cables are made from 2 up to 61 cores. How many spare cores to include is covered in the control cable core-count and spare-core planning guide.