Ambrosia Maple gets its name from a beetle. The beautiful blue and greenish streaks that you see in the wood are caused by a fungus that the ambrosia beetle carries on its legs. When the beetle chews its way into the tree, the fungus enters the xylem and floem and stains the wood. It happens in three dimensions, however, it is mostly a two dimensional effect on lumber, except when you get to the edge of a board. Dramatic effects are seen when bookmatching, exemplified by the endgrain cheeseboards above.