Unknown Shrimp

Divemaster Nus Lobbu photographed these well camouflaged, almost ghost like, shrimp couple atop a coral in Lembeh. What may they be?

Snapping/pistol shrimp, afaik.

Thank you, Wolf Eel.  Following your suggestion, I find this:
 "Alpheus is a genus of snapping shrimp of the family Alpheidae. This genus contains in excess of 291 species, making this the most species-rich genus of shrimp. Like other snapping shrimp, the claws of Alpheus are asymmetrical, with one of the claws enlarged for making a popping noise. Wikipedia".  
 Nus Lobbu has added it may be an Alpheus Sp. 2, as yet undescribed, snapping shrimp. This shimp does not quite match the photo in Humann and Deloach, which shows it with reddish claws and "head" with white spots and a colorless body, in 'Reef Creature Identification-Tropical Pacific', p 85. But the blue-purple color of the entire body of Nus' shrimp most likely is from its feeding on the coral of that color. 
 More suggestions are welcome. 

Hi Elias

I have a similar photo (but just one shrimp) taken in Lembeh. It is not on coral but on a colonial ascidian inside which it lives I believe. It has not been described but for the time being is considered to be Periclimenaeus sp. I found a specialist in the Netherlands who provided this the ID for me. The photo has since been used by Andrey Ryanskiy in his ID guide to Coral Reef Crustaceans. Hope this helps.

As requested in your PM, here is my photo of this shrimp - it is a pretty big crop from the original so hope it looks OK. I have only found one other photo and it was on the same species of ascidian and taken in Lembeh. I should have been a little more clear, the shrimp expert's ID was tentative but he was definite that it has not been scientifically described.

"Not been described", that about summarizes this shrimp as far as one can tell.  
In the "olden days" one would dive back in with a small jar, collect the shrimp and bring it back to send to an expert for classification. Several divers I know did, and still do, this with nudibranchs. But in Indonesia nowadays I have been told a foreigner can get in bad trouble as it is illegal to take and export a marine invertebrate. I looked this up and was unable to find a clear answer. 
One of my buddies sent a beautiful undescribed nudibranch to a top expert, who had his assistant describe it,  the assistant then proceeded on her own to name the nudi after her favorite niece.  My buddy is still fuming...