I think its not such a great idea to change from color to monochrome! I think its a better idea to make a red frame around something which is active! Or something in that direction! But I am still collecting ideas regarding icons!
My main goal is to go as self explanitory as possible..and as common in 3d as possible! For me the design and function of an icon is good if everyone knows what it means without opening a manual! That isnt even just valid for 3d..its valid for every product! If you know how to use it when you grab it..its well designed!!!