Magnitude and colour evolution of 12P. Top: light curve of comet 12P with TRAPPIST in the Rc band with an aperture radius of 5″. Upper arrows indicate saturated images that could only yield an upper limit on the magnitude. The detected outbursts are indicated with red tick marks. The vertical dashed line indicates perihelion. Bottom: colour indices from the BVRcIc filters. Reference colour indices for long-period comets (LPC) from Jewitt (2015) are indicated as horizontal dashed lines. No colour indices are available for the post-perihelion survey. The vertical dashed line indicates perihelion.