My toddler loves to sort things, and he feels so proud of himself when he correctly assigns coloured objects. So we do a fair amount of colour sorting with him at the moment. Above he is putting coloured bricks from a push-along trolley onto some coloured plates we have.
One way in which I’ve managed to involve my preschooler in this too is to make a ‘colour-sorting race’! Essentially, I collect together a basket of different coloured toys (that match the coloured plates we have), and then we time each other running from the basket to the plate with one toy at a time. My toddler enjoys the matching and happily trundles around assigning objects, my preschooler loves to use the stopwatch and make me run and tell me to ‘go faster Mummy’! A good activity for the three of us.