Finally I have achieved colour pooling! In the end I had to order a specific yarn (Red Heart Super Saver – Sunrise) which I’m sure cost about 3x as much as it would if it were stocked in any shops in the UK. But I looked everywhere – all the shops that sell yarn near me (and near a few other people too) and there’s plenty of self striping yarn but nothing that would pool into argyle.
The colour change in the yarn itself is very simple – quite a long length of red (purple fading through red to orange) then a short section of yellow, green, blue and that’s it – rinse and repeat.
It still took quite a few attempts to get it to work – moss stitch was the key I think – and even now it’s not just mindless crochet – you have to constantly adjust tension to make sure things line up as they should with the rows below. I’m not sure what I’ll make of this in the end – maybe a shopping bag.