This hat is made with the crochet technique, with the centered single crochet, changing the colors with the tapestry fair isle technique following the chart. Worked in the round, from the center of the top part making increases and changing the color following the chart.
In this file you can find the charts to make the sizes from baby to adult. The charts are similar but not equal depending on the sizes.

You can find the free video tutorial to learn how to make this hat here https://lanasyovillos.com/en/accesories/izei-hat/