I have grown out highlights and some greys, and I would like to dye it all to match my natural colour. I had a horrible experience dying my hair before when I overestimated the darkness and chose an almost black colour which looked terrible and I spent the next two years growing it out 
I have pale skin and blue eyes so I think I need to go for a cool tone? It's just so confusing as there are so many brands and colours! I want to try semi-permanent first to avoid my previous mistake.