An aerosol-generating article may comprise a liquid storage portion containing a liquid aerosol-forming substrate, and a hydrochromic material provided on the liquid storage portion. The hydrochromic material has a first colour when in the presence of or when in contact with the liquid aerosol-forming substrate and a second colour when in the absence of or when not in contact with the liquid aerosol-forming substrate. An aerosol-generating system may comprise the aerosol-generating article, an aerosol-generating element, and an aerosol-generating device. An aerosol-generating device may comprise an electrical power supply, an electronic photosensor, and a controller configured to control a supply of electrical power from the electrical power supply based on a value of an optical property sensed with the electronic photosensor.