Atyopsis moluccensis.. bamboo or flower shrimp. Often the lighter coloured ones are called mountain shrimp but of the few I've had, all changed to the dark brown colour of my wood pieces not long after I got them. Natural camouflage allows them to change colour to some degree, though not instantly.
Edit. Please provide a nice current for the shrimp to feed in. They are filter feeders, and if you see them scavenging the bottom with their fans, they are very, very hungry. If the tank is not well aged, you can supplement their diet, with green water, golden Pearls in the 5-50 micron size, or flakes ground to the finest possible powder, like baby powder. Or a pinch or two of bakers yeast, allowed to soak in warm water for ten or fifteen minutes with a pinch of sugar, stirred up and poured in the tank. All these they can filter out of the water with their fans.