Color graphics are amazing. I use it all the time and it never fails me. of course just like any colour or bleach - if you've got a natural root and heavily coloured ends youre looking at 2 mixtures anyway to achieve an even result. It isn't a miracle worker but does make life a lot easier sometimes! Saves u so much time not having tone.
Dream age is the single best product for gray coverage I have ever used. Never let me down no matter how stubborn the grey is. They're expanding the range all the time . I have phased out the 500/extra coverage range now. not a patch on dream.
But also the socolour main range have 2 pages to the chart, the first page being the natural gold etc - they cover uto 75% grey.. the next page being the reflect/fashion colours cover unto 50%, I use 10n 20vol on a 65yr old lady with 75% grey and its perfect. So don't worry too much with them, they will rarely let you down I assure u! If they do id question the human method before blaming the colour. We're a matrix salon through and through now - after trying sooooo many brands.. I'm happy!
Hope that helps you, Laura x