Okay, I've went and updated this somewhat.
Codes Yellow and Orange mean that members who want to join must be approved by Administrators, as well.
Green: Normal condition. No risk. New members are immediately registered.
Blue: Guarded condition, general risk. Review security measures. Registering members must activate their accounts through e-mail.
Yellow: Elevated condition, review security measures and implement as needed. Registering members must be approved by admins.
Orange: High risk, user investigation started, review site security. Registering members must be approved by admins.
Red: Severe risk. Lockdown started and methods from previous codes implemented. Registration is entirely disabled.
Code Black: Imminent risk, total lockdown and investigation. Staff review and security measures reviewed. All emergency measures implemented. Registration is entirely disabled.