Most of bamboo boards was pressed by  three grains,Flat grain,Edge grain and End grain.It has two colors,one is light,which is the natural color of the bamboo,the other is dark,which is steaming,exstracting the water and sugar of the bamboo,carbonizing it.Both colors are permanent.

Flat grain approx. 5/8" wide is from the face of the pole

Edge grain approximately 1/4" wide is taken from the side of the split pole

End grain is the cross section of the pole.