Hi there, I can help a little, I wear the #22, which I find to be a little less "yellow" than the #613, and I have sucessfully gotten it to a nice cool, whiteish blonde by using the redken EQ toner in platinum ice, but you need to be really careful with it, I make sure the hair is damp, towel-dried, and then applying the toner via a squirt-top container, and combing it through really quickly, it's best if you have someone help you if you can.
You need to wash it off in like less than a minute, even less sometimes, it depends, best to do a strand test before, as all hair is different. You can also use the purple toning shampoos etc, they work ok too. I know people have used bleach/colour kits, but personally I don't like re=processing the hair, the blonde shades have been through enough torture

and I like my hair to stay soft and silky as my own hair is really sleek too.
My tip is to just always do a strand test before you try anything, even the shampoos, as you can easily turn the hair purple or grey

and it's awful to wreck beautiful new hair, take it slow and just try a few things, you will manage to get the gold out, or if all else fails, take to a good salon who know extension hair and let them do it for you, I have also done that with good results. Goodluck
