Injector are easy to understand if you read the book it tells you what each letter and number stands for then the rest you adjust with timing example N stands for needle valve C stands for crown valve the list goes on,
Our 8V71 book is vintage 1963, and it has both needle and crown valve overhaul procedures described - but the list doesn't go on any further than that.
In our book the Nxx's are the needle valves, and the crown valves actually have no letter shown as a prefix. Just "55" and "N55" for example.
No mention in our book about the other letter prefixes, and actually no mention about the practical difference between needle and crown valve, and why / when you would use one or the other.
And no mention at all about color tags.
It would be great if an online reference for this stuff existed somewhere. I imagine a more recent Detroit Diesel book might have more info too.