Dia Light is L'Oreal Professionnel's acid, ammonia-free demi-permanent colour. It's used for toning, glossing, refreshing faded colour and softly blending grey without lifting the natural base. It gives a luminous, translucent, tone-on-tone result that leaves the hair shiny and conditioned, and fades gradually with no harsh regrowth line.

Dia Light is mixed with L'Oreal Dia Activateur (the liquid developer), typically at a 1:1.5 ratio, and develops in around 20 minutes. Choose a lower-strength Activateur for the gentlest tone-on-tone results, following the professional L'Oreal instructions.

Dia Light blends and tones grey rather than fully covering it, making it ideal for softening grey and adding shine on hair that isn't fully white. For higher percentages of resistant white hair, Dia Richesse or a permanent colour such as Majirel or INOA will give more complete coverage.

Both are L'Oreal acid demi-permanent colours. Dia Light gives a more luminous, translucent, high-shine result and is popular for toning and glossing, while Dia Richesse gives a slightly more opaque, natural-looking finish with stronger grey blending. Both are ammonia-free and mixed with Dia Activateur.