User blog comment:B214/Question and Answers 6/@comment-203.59.190.84-20170604025234/@comment-30924344-20170604114255

Unless there's a colour illustration of normal Tannin with blue scales, his colour is purple. This could just be a mistake by Ishibumi to not remember Miyama coloured Tannin in purple in V5 or maybe Ishibumi yet again, changed the colour of a character's appearance. It's 50/50 at the moment so we can't say Tannin's actual colour now is blue.