The recipes call for bars of castile soap, but they're usually using dr bronners (mostly coconut with a few other oils) or Kirk's Castile (coconut).
That said, my current laundry soap is mostly olive oil castile. I made some soap for laundry a while ago, it was probably 50% lard, 25% coconut and 25% olive oil (0% superfat). And when I went to make up the laundry soap, I used the wrong bar, I used a 100% olive oil bar. Got my clothes clean. I discovered my mistake a couple days later and I was worried that it wasn't strong enough, so I added some of the original lard/olive/coconut soap to it. Works incredibly well, but I am very sensitive to coconut oil, and I think it may be causing some skin irritation even in such a small amount. I may make some again and use only the olive oil soap.