Sixteen colour wool farm

The first wool farm that runs with nobody nearby. Sixteen sheep, one per dye colour, sit in individual dirt cells with an observer watching the grass block each one is eating and a dispenser of shears above it. What is new is not the shearing but the grass: it now spreads in any loaded chunk, so with a chunk loader or spawn chunks the farm keeps producing while you are elsewhere, which every earlier wool farm could not do. A hopper minecart railway collects the wool and a second railway refills the dispensers with shears.

If the sheep only shear when you flip the lever, the lever is supposed to be off. jrokingamez and ToastyTM both say leaving it off lets the observers trigger on the grass change instead, and DailyDrDonut confirms that fixed it.
SnowBlind-vl1jy warns the shear railway does not distribute evenly. One side fills every dispenser and hopper before the other side gets anything, so it needs far more shears than you expect before it looks like it is working.
dracconis69 shrinks it from 5x5x26 down to 5x5x17 so it fits inside one chunk instead of two, by facing the dispensers outward and running one hopper into the top of each rather than two.
The farm sorts the wool by colour and then Rays throws it all in one chest. He says in the replies you can keep it separate with hoppers under each rail run, he just did not want to pay the hopper cost.
Feed the shears from an iron farm through a crafter and it never needs topping up. This is the top comment on the video, and believer218 adds a comparator so the crafter only fires when it is full.
On Bedrock, JamesRobinson01 has it running on 26.23 with one change, looping the collection track into a circle over extra hoppers rather than using the automatic minecart stop.