There's an international standard, ISO 6009, which dictates the color of the plastic for hypodermic needles. Each color is assigned to a different gauge so that hospital workers all over the planet can just grab the right color and know it's the right gauge.
24g are "Medium Purple", while 13g are just "Purple".
24g Medium Purple includes PANTONE colors 666 667 and 668.
13g Purple includes PANTONE colors ... I have no clue cuz I can't find a leaked copy of ISO 6009 which lists these and I'm not spending $45 to buy the fucking standard.
You can see PANTONE 667 here: PANTONE Colour Chart | www.PANTONE-colours.com (YMMV, actual color different from what you see on your screen)
If you'd like to learn more about the PANTONE system, why it exists, and what it's useful for:
View: https://www.youtube.com/watch?v=xj6GikPbhdQ
View: https://www.youtube.com/watch?v=JF8UziDHqZo
Thank you. I was thinking it might be something along these lines.