What information is written on the ACH helmet band, and what color should it be?

You won't find a reg, this is based on unit SOP. Units may have completely different standards. I would direct this question to your NCO leadership. You may get incorrect information on here.

Don’t put anything till you to to your unit! Units, brigades or divisions have their own standards about what they want it to look like.

It's all based on your units TACSOP, I'd ask your first line.

What they all said...lol every unit has their own SOP's

Unit SOP

Every unit is different.

Usually unit specific. Commanders can specify undesignated specifications to unaddressed uniform issues with a SOP or memo. also check the DA Pamphlet as well as the regulation. Or get with your NCO support channel to ask the 1SG or CSM.

It’s usually last name, battle roster, and blood type. You need to ask your NCO the order in which they want it.

All of that is per your unit SOP

As stated above, you won't find a regulation on it. I collect helmets that have been down range, and they are from every branch of service, but mostly focused on the Army. That being said, I've seen everything on cateyes and located everywhere.

Most will have your Name, Blood Type, and Battle Roster Number in varying forms. Some units have guys write them, others have them sewn on the cateyes directly, while others have them sewn a material, then sewn on to the band. Other units don't write anything at all on the cateyes, but that tends to be earlier in OEF/OIF.