This is called the "Tie Dye Beanie Cap"
But...it doesn't really look traditionally tie-dyed as there's no rainbows, swirls or the signature 'marks' of the tiedye process. It's more of a 2 tone mottled blue color for the knit beanie hat. The only Sonic element here is an all-embroidered classic style Sonic face on the front of the roll/flip up part at the bottom of the cap.
Its an ok item if you need something somewhat Sonic for the winter. Is this a SegaShop item, or is it Spencers?