I’ve been buying packets of KoolAid. It’s a powder drink which you dilute to taste, and comes in many flavours.
The flavours are chosen mainly for their colour, so lots of red colours, depending on what’s available in the shops.
I soak the yarn in lukewarm water with a splash if liquid detergent (washing up liquid), then on with the rubber gloves.
Then, I used a packet (or more) of the powder in a microwave able bowl, and stir it until all the powder is dissolved.
Rinse the soaking wool in lukewarm water, then put it in the powder mixture.
Put the bowl in the microwave, and I let it run for 15 minutes. What you need is for the water to be clear, which means the yarn has dissolved all the colour of the dye.
Let it cool, then wash and rinse in lukewarm water. Remember to squeeze the yarn, not rub it or it will felt/shrink!
Leave the yarn to dry, and marvel at the new colour.