Level 6 corresponds to a dark blonde on the universal colorimetry scale (1 = black, 10 = lightest blonde). It measures the lightness or darkness of hair, independent of the reflect.
The red (.6) reflect is the most intense and vibrant. It adds a pure red undertone creating striking, high-personality results. Requires frequent maintenance as red is the pigment that fades fastest.
Each brand codes level and reflect differently. The table above shows how the major professional brands name this same shade: level 6, red reflect.