Will this cover my grey hair completely, and how does the mahogany reflect behave on white strands?

Permanent cream dyes at level 5 with a .5 reflect are formulated to deposit enough pigment to cover resistant white hair while the mahogany tone prevents the "helmet" effect of a solid dark brown. On 100% white strands the colour will take true to the swatch — a warm, red-brown that reads as a natural-looking depth with a subtle glow. On salt-and-pepper hair the already-pigmented strands will shift slightly warmer and darker, while the white strands become the brightest points, creating a natural-looking highlight pattern. If you have more than 70% white hair and want a completely uniform result, you may need to pre-pigment (apply a warm copper or gold demi-permanent first) or choose a neutral/natural series (e.g., 5.0) for the root area and use 5.5 only on the lengths. The creamy consistency helps here because it clings to the hair rather than dripping, giving you more control to saturate resistant grey at the hairline and temples. Re-growth touch-ups every 4–6 weeks will keep the blend seamless; the mahogany reflect fades to a warm caramel rather than an ashy green, so the line of demarcation stays softer between salon visits.