[vectorit]

I was just wondering if someone can educate me a little.

I have a D44 8 lug axle out of a '72, and it has the yellow Spicer knobs.

Just wondering what the significance is to the yellow and blue knob?
Is one for a particular model, such as GMC or Chevrolet?

I know the red one is from a Ford application.

It seems through my research that the blue ones are more scarce, and tend to bring more of a premium over the yellow ones. Is that because they are just more uncommon, or is there another reason?