When I am at halo reach armour customisation, after I select helmets, the items are not separated as Unlocked/Locked as I see to happen with other armour types menus. I can select them and go to the submenu with the helmet’s variants where I see all variants locked. If this is intended please still make locked helmets buttons visually different so I can easily see my available options. I am playing from Pc through Steam
In some cases you will unlock one variant of a helmet and not others. This is why the helmet is showing as unlocked - you have unlocked at least 1 variant.