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This specimen was identified by David W. Behrens as a version of IPN Rostanga sp. 1 at page 191:
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books.
Gig Harbor, Washington. 426pp.
Let me quote the description: "This species is unusual among species of Rostanga in having a white to pink body color."