The amount of ink in each cartridge is shown by icons in the front panel.
Each icon refers to a specific cartridge, as shown by the colored marks below the front panel.
The icons refer respectively to the Black, Cyan, Magenta and Yellow ink cartridges.
The amount of ink corresponds to the height of the "gas gauge".
When a cartridge is low on ink, the last block of the corresponding icon flashes. If the complete icon flashes, the cartridge is completely empty and must be replaced to allow printing to continue.
If all the icons flash, there is a fault in the ink supply system.