The client card
Formulas, notes, and history in one place — and who can see what.
Every client has one record that carries their history with your salon: appointments, payments, messages, notes, and colour formulas.
Colour formulas
Formulas are their own thing on the card, not a note you have to find again. The point is repeatability — write the mix down at the chair while you still remember what you adjusted, and next visit is a read rather than a reconstruction.
Notes
Notes are for what the formula doesn't capture: how they like it dried, that they're growing out a fringe, the conversation you'd rather pick up than restart.
Client records are personal data and you're responsible for what's in them. Keep notes to what you need to do the service well — anything you wouldn't want to read aloud to the client themselves doesn't belong on the card.
Duplicates
The same person booking twice with two email addresses is the normal way duplicates appear, and it's usually noticed just after an import. You can merge two records into one rather than deleting the one with the history on it.
Messages
Messages with a client are a single thread on their card. When they reply to one of your emails from their own inbox, the reply lands in that thread rather than in your personal mail.