Zero Amm uses the Igora level-reflect format: 7-42 = level 7, beige ash.
- Level (1-10): depth, from black to ultra blonde.
- Schwarzkopf suffixes: -0 natural, -00 natural extra, -1 cendré, -2 ash, -3 matte, -4 beige, -5 gold, -6 chocolate, -7 copper, -8 red, -9 violet.
- Two digits after the dash (like -76): the first is the primary tone direction (the dominant shade) and the second the secondary, per Schwarzkopf's US wall chart. With the same digit twice (-88, -11), both directions are the same reflect: judge its strength from the swatch.
Same logic as Igora Royal, so keep the house quirks in mind: -5 is gold and -7 is copper. Every house prints its own key.