Toning sock yarn

I want to knit these socks some time soon. I need two skeins of sock yarn, on the heavy side – the pattern asks for Socks That Fit sock yarn (100% wool) 350 yds/320 m per 100 g/3.5 oz. Natalie’s Merino yarn, Hug, looks about spot on, if I ever manage to score some before it all sells out…

Ideally I would like two toning yarns, both of them slightly shaded. I’d like subtlety rather than stark contrasts.

So, anybody know of a yarn that meets my requirements? Please tell!