I'm quite a beginner so I don't touch yellows 😂
₿ack in my uni days we would warm up with a “yellow” then go to a double blue it was like playing with a rock til it warmed.
This says i was using double yellow
https://www.squashpoint.com/blogs/blog/how-to-choose-the-right-squash-ball/
Discussion
Its good practice once your strength and technique are stronger. it was exercise for me and a friend he was technically better but i could travel faster.