Found this on Ask.com I searched under sewing machine needle color code and got a few different answers based on the brand. I learned something new today!
Singer color codes
Singer colors its needles with a system of color codes which indicate the needle's type:
Shank color Point type
red regular, for woven
yellow ball, for knits
blue heavy-duty, for denim
brown chisel, for leather
Shoulder color Shaft size
green 9 (thinnest)
orange 11
blue 14
purple 16 (thickest)
Kenmore color codes
Kenmore colors its needles with a different system of color codes which indicate the needle's size:
Shank color Shaft size Shaft size (europe)
blue 11 75
orange 12 80
red 14 90
purple 16 100
green 18 110
Schmetz Color Codes
The colored band on some types of Schmetz needles indicates the needle type. [2]
Shank color Type
yellow Stretch
blue Jeans
green Quilting
red Embroidery
purple Microtex (sharp)