My youngest daughter Sofie is just growing up to fast. Her wollen socks are getting to small. And she is already cold going out into the rain with her big rubber boots. SO then I have made a special pair for her in thin sock yarn that changes colour.
Since she is so long and slim, I chose to make a kind of rib-socks, but make them smooth under the foot.
The colour changing in this yarn was different from what I was used to - so I gave up creating two similar socks, but created them more on the basis "Same Same but Different"