Here there is a guide made by the FW team:http://www.forgeworld.co.uk/downloads/product/pdf/h/Horus_Heresy_Painting_Guide.pdfHope that can help you :)
As far as I can see it looks like they still use the paints from the HH painting guide: http://www.forgeworld.co.uk/downloads/product/pdf/h/Horus_Heresy_Painting_Guide.pdf
http://www.forgeworld.co.uk/downloads/product/pdf/h/Horus_Heresy_Painting_Guide.pdfFrom their own Downloads page. It's a mix that is complicated. And just gets more complex as you highlight it... :s
Not sure if anyone mentioned the horus heresy painting guide yet, have you checked that out?*Ducks and runs*The Sons of Horus color scheme shifted throughout the heresy from a light seafoam green to a dark, almost black-ish green, so almost anything you choose will be 'right'! :)
Thanks to everyone for pointing me to the Forge World painting guide, I had no idea it existed. The green shade seems quite complicated.