Homemade cards are increasingly being rejected at facilities across the country, and the reason has nothing to do with the sentiment behind them.
Correctional facilities have discovered that hand-made cards and letters have become a delivery method for drugs. The technique involves saturating paper or using ink that has been laced with synthetic drugs. When the paper or dried ink is licked or touched, the drug activates. It sounds extreme but it is real, documented, and widespread enough that facilities have responded by cracking down on anything hand-crafted coming through the mail. The federal system in particular has moved aggressively against homemade cards, and many state and county facilities have followed.
The ink color question, whether blue or black is required, has largely become secondary to the bigger issue of whether handmade items are accepted at all. Even a carefully made card with standard ink can be rejected simply because it is not a commercially produced product that can be verified as unaltered.
The safest path is to use a service that facilities already recognize and trust. InmateAid offers postcards and greeting cards that are printed professionally and mailed through USPS in envelopes that mailroom staff recognize on sight. They know where the mail is coming from, they know it has not been tampered with, and it moves through the system without the scrutiny that a homemade card now attracts.
Your message gets through. That is what matters, and InmateAid makes sure it does.