The FCOM states something like:
Top of amber bar indicates minimum manoeuvring speed. This airspeed provides:
• 1.3g manoeuvre capability to stick shaker with flaps down
• 1.3g manoeuvre capability to stick shaker or VREF+80, whichever is less,
with flaps up at or below 20,000ft
• 1.3g manoeuvre capability to low speed buffet (or an alternative approved
manoeuvre capability as preset by maintenance) with flaps up to 20000ft