Dia richesse - cover first greys, lifts one level with 15 vol, subtle reflects, introduction to colour, darkens 4 levels with no need to precolour, can get more intense results on light/ pre lightened bases, can be used as toners if you want a more dense result.
Dia Light - acid based colour (closes cuticles) the clear will close cuticles to lock in a colour and add shine, good for colour correction, extremely subtle on natural hair (more for gloss than reflect) nice as toners but more subtle and light then dia richesse. Also good to use when pre pigmenting
hope that helps