Size (circumference measured around the heaviest part of the foot, zero ease)
Adult small (21cm), Adult medium (23 cm ) , Adult large (25 cm )

Note: This pattern is very easy to adapt. Every 2 cm, you increase/decrease 6 stitches (one repetition of chart A) around the leg. When it comes to the foot, a multiple of 12 is easier, allowing you to have an exact multiple of 6 for the instep stitches and the same amount for the sole. But, in case you only have a multiple of six, you only have to knit Chart A + 3 sts of this chart on the instep and Chart B + 3 sts of the same chart on the sole.
Example: for a newborn socks size (9 cm circumference) you will need 30 stitches.
Leg: 5 repetitions of Chart A
Foot: instep (Chart A ) twice + 3 stitches of Chart A, sole (Chart B ) twice + 3 stitches of Chart B

Material
Yarn: 100 (110 , 120 ) g of sock yarn in at least 5 different and contrasting colors. In my pattern, I used 6, a different color only for the heels, but you can always use the same color you use for the cuffs and toes.
Needle: 2.5mm (circular 100cm long or DPNs, your choice)
Darning needle for finishing

Gauge
In stockinette stitch, knitted back-and-forth, washed but not stretched:
10 cm = 32 sts (rows are not relevant for this pattern)

Chart A, knitted in rounds, washed but not stretched:
10 cm = 38 sts (rows are not relevant for this pattern)