This looks similar to Discodoris lilacina but the colors do not seem to match that well.
It seems to match the description of the Discodoris in the latest ed. of Humann and Deloach, page 312, bottom right - listed as Undescribed.
what do the experts think?


Looks like Atagema sp. 6 (page 186) in Indo-Pacific Nudibranchs and Sea Slugs, but these guys are tough...
Cheers,
Marli