Laundering blowouts...

Elle • Snap: MochiBunn
We EBF and our son has had a couple blowouts. I can't get the yellow color out of a couple pricey outfits of his! 
I soaked immediately, washed with Castile soap (our usual) and there was still a spot so I rewashed with Dreft. 
Yellow spots are still visible on the inside and on a white blanket....
How in the world do I get these blowout spots out?!