It helped me to decide what O-rings were right for me, and they weren't the ones I expected! The package arrived exactly as described. Took me a second to find, if it was a snake it would've bitten me, but on the front of the package under the barcode is a handy little chart that helps differentiate the hardness of the o-rings based on color. You can actually see the chart in the 3rd image for this item. As far as telling size, i just looked at them side by side after grouping by color.

A variety of o-rings is great. However there is a major flaw with how they are labeled in the way that they are barely labeled. I thank chase for providing a basic a table to the sizes and hardnesses (something you would think that would be included in a sample package such as this)

It should have been considered when putting this product together, because it may not be immediately clear to interested buyers, that it can be distinguished what O-ring you like to purchase more. Clearly buyers do not know what they want when they purchase this. This sample kit helps determine that. But the product packaging is slimmed down and lacks a complete color-coded table for sizes and hardiness. This could help alleviate confusion and improve the customer experience. For people who don't quite understand, this might help you.

For MK Pro brand O-rings, colors indicate hardiness and thickness. The hue (Yellow vs Pink) relates to the hardiness, and saturation (Light Pink vs Dark Pink) relates to the thickness.

Yellows are 30A.
Reds are 40A.
Greens are 50A.
Pinks are 60A.
Blues are 70A.
Purples are 80A

Examples:
For 30A 1.5mm this is the Darkest Yellow.
For 30A 2.0mm this is a Dark Yellow.
For 30A 2.5mm this is a Bright Yellow.
For 30A 3.0mm this is the Brightest Yellow.

The rings themselves seem fine. But it's hard to distinguish hardness because there basically isn't a useful guide that maps color to hardness. What the product needs is a normal table that maps color to hardness, or color to hardness and thickness.