Here,s one picture where you can see the cliffs, on a day with some clouds.
The stone is yellow, the dirt on top is a little more brownish. On a bright sunny day the cliffs look more white specially when the rock is dry.
But as D-day was preformed at a windy, clouded day I'd suggest you keep to the yellow seen in the picture here.
The small pebble beach right below where this picture was taken from has very dark grey, almost black stones.